Celebrities You Forgot Starred On Grey's Anatomy

Plenty of stars have been made through "Grey's Anatomy," including Katherine Heigl and Ellen Pompeo, whereas other stars, like Patrick Dempsey, were already quite famous by the time they joined the cast of the legendarily long-running medical drama. The series, which began in 2005 as a modest mid-season replacement created by Shonda Rhimes (now a legend in her own right), tells the story of a Seattle hospital that sees all sorts of unlikely and incredible medical cases ... which might not be particularly realistic but are plenty compelling all the same.

Aside from the core cast, many other actors passed through the halls of Seattle Grace Mercy West turned Grey Sloan Memorial Hospital over the years. And you might be surprised to learn about some of the incredibly famous faces who guest-starred on this beloved show. Here are just a few of the celebrities that you totally forgot showed up on "Grey's Anatomy."

Throughout her career, Elisabeth Moss has made a serious name for herself in small-screen prestige fare like "Mad Men" and "The Handmaid's Tale," as well as spooky movies like "The Invisible Man" and "Us," solidifying her as one of the most in-demand actresses of her generation. However, it would make sense if even her biggest fans forgot that she appeared in a single episode of "Grey's Anatomy" way back in 2007 (an episode penned by future "Bridgerton" creator Chris Van Dusen).

In the Season 3 episode "My Favorite Mistake," Moss plays Nina, the bossy, protective daughter of a patient named Cathy (Catherine Dent), who has an extraordinarily rare disease — fibrodysplasia ossificans progressiva — where her muscles turn to bone at the slightest touch. Though the patient has an elaborate dollhouse in her room that Nina claims her mother built for therapeutic reasons, it's clear that Nina built it herself and is unprepared for the possibility of her mother's death. When her mother doesn't survive the surgery, Moss plays the beat perfectly, even as Cathy's doctors explained that the ill woman was ready for death. It's a small role, but Moss is the perfect person to play it.

Known for projects like "American Horror Story," "Run," and "Ratched," Sarah Paulson has become one of the most acclaimed performers in Hollywood, known for her all-consuming commitment to her roles and the way she's able to disappear into a huge variety of characters. However, long before finding widespread fame, Paulson popped up during a Season 6 episode of "Grey's" called "The Time Warp," playing one of the show's most influential doctors — Dr. Ellis Grey — in a flashback.

The mother of series lead Meredith Grey (Pompeo) and a trailblazing surgeon in her day — only to fall ill with early-onset Alzheimer's — Ellis is one of the show's biggest icons, so it makes sense that a performer like Paulson would play her. In a flashback relayed by Ellis' colleague and former love, Dr. Richard Webber (James Pickens Jr.), viewers watch as Ellis and Richard — who are secret lovers — try to help a patient with GRID, which is what medical professionals once called AIDS. There are several other flashbacks in the episode that don't feature the actress, but Paulson's presence elevates the entire hour.

An incredibly versatile actor, John Cho can do anything, from "high" comedy like the "Harold and Kumar" movies to J.J. Abrams' "Star Trek" adaptation to acclaimed indie flicks like "Searching" (which made Cho the first Asian American actor to lead a Hollywood thriller). However, just a few years after the first "Harold and Kumar" film, Cho also appeared in a single episode of "Grey's," playing an incredibly tragic role.

In one of the last episodes of Season 2, "Damage Case," Cho is front and center as Dr. Marshall Stone, a surgical intern at a different hospital suffering from extreme sleep deprivation after a long shift. And as he drives home from work, he closes his eyes for just a moment, falling asleep at the wheel. As a result, he causes a massive car crash that ultimately kills a young pregnant woman and injures her entire family, as well as Marshall. It's a devastating turn that finds Marshall begging for forgiveness from the girl's family, and Cho, a phenomenal actor, completely pulls it off.

Millie Bobby Brown might play a huge, pivotal role in a Season 11 episode of "Grey's," but amazingly, you don't even see her for most of the episode, which is a testament to Brown's sheer talent as a young actor. One of the breakout stars of Netflix's "Stranger Things," who's also appeared in original films on the streamer like "Enola Holmes," Brown is a phenomenal performer who manages to hold the audience's attention in the 2015 episode "I Feel the Earth Move."

After an earthquake strikes Seattle, several doctors get a frantic phone call from a young girl named Ruby (Brown), whose mother has just passed out and is having a serious medical emergency. As they try to find her location while coaching Ruby through helping her mom, Ruby's cell phone starts to die, making the situation that much more dire. Ruby eventually makes it to the hospital and saves her mother, but even off-screen, Brown's presence is unforgettable.

Known for fare like "A Walk to Remember," "The Princess Diaries," and "This Is Us," Mandy Moore is a beloved mainstay of the big and small screen. And that made it incredibly exciting when she appeared in some of the very best episodes of "Grey's Anatomy." 

Audiences first meet Moore's Mary Portman in the Season 6 two-parter "Sanctuary" and "Death and All His Friends," which sees the hospital undergo a crisis as an active shooter roams the halls, taking out doctors and patients alike. As a woman awaiting a colostomy bag reversal, Mary survives the shooting alongside Dr. Miranda Bailey (Chandra Wilson), helping the general surgeon as they try to save Dr. Charles Percy (Robert Baker), who suffers a gunshot wound during the massacre.

However, Mary's eventual fate is absolutely heartbreaking. In Season 7's "These Arms of Mine," an episode presented as a documentary about the hospital post-shooting, Mary finally gets her surgery ... and never wakes up again. Moore's Mary is a compelling, great character, and it's terrible to watch as she misses out on her happy ending.

The doctors lose a lot of patients throughout "Grey's Anatomy," but luckily for Demi Lovato's Hayley May, resident surgeon Dr. Alex Karev (Justin Chambers) takes a huge leap to help her ... and ends up saving her life in the process. A Disney Channel star turned musician and actress, Lovato is known for everything from "Camp Rock" to "Eurovision Song Contest: The Story of Fire Saga," but hardcore "Grey's" fans remember them playing a seriously disturbed teenage girl threatening to take her own life.

Brought to the hospital by her concerned parents, Hayley is a wreck, screaming and threatening to harm herself — all while insisting that she's "not crazy." Karev manages to convince her not to hurt herself, telling her that he believes she isn't crazy, and though he's met with plenty of doubts from his colleagues, he turns out to be exactly right. As it turns out, Hayley has a bizarre disease where she can hear all of the functions happening in her body at all times, and living with it is making her seem completely insane. But once Karev figures out the treatment, Hayley is saved. "Grey's" has seen plenty of explosive guest turns, but Lovato's is unforgettable.

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"Grey's" has seen its share of completely insane medical oddities, but one of the most unforgettable is definitely from Season 2's "It's the End of the World" and "As We Know It,", where the hospital has to deal with a bomb in a body cavity. After two military re-enactors make their own bazooka, one of them gets shot in the chest, but the homemade explosive never exited the man's body, meaning that the doctors trying to save his life are in danger of being blown up at literally any moment.

Involved in all of this is a young EMT named Hannah — played by "Addams Family" breakout Christina Ricci — who's left literally holding the bomb itself after reaching into the man's chest to stop the bleeding, terrified and unsure of what she should do. Hannah ends up abandoning the man in a moment of panic, leaving Meredith to step in and fill her shoes, but in the end, the doctors still thank her. Despite fleeing, she still saved the man's life.

Throughout the series, Richard Webber struggles with plenty of family issues, including his niece, Camille, who suffers from advanced ovarian cancer after being diagnosed at just 14 years old. Though she's later portrayed by Camille Winbush in Season 4, when viewers first meet Camille in Season 2, she's played by a super recognizable face: MCU star Tessa Thompson.

Thompson — who also appeared in shows like "Veronica Mars" around this time and eventually moved on to huge projects like "Creed," "Westworld," and "Thor: Ragnarok," — showed up in the two-part Season 2 finale, "Deterioration of the Fight or Flight Response" and "Losing My Religion," after Camille falls ill at her prom. To try to make it up to her, Richard demands that the hospital throw a prom that everybody in the hospital must attend. Though Thompson doesn't actually appear in a ton of scenes throughout the episodes, she definitely steals the spotlight every time she does.

Christina Ricci is a huge part of the "bomb in the body cavity" episodes of "Grey's Anatomy," but she wasn't the only guest star in that story arc. Alongside Ricci, Kyle Chandler also plays a pivotal role in the two-part installment as the leader of a bomb squad desperately trying to save the day. Known for turns in everything from "Friday Night Lights" to "The Wolf of Wall Street" to "Game Night," Chandler is a beloved and versatile performer, and he brings his considerable talent to the two episodes as Dylan Young.

Tasked with helping the surgeons navigate the homemade bomb, Dylan is fairly prickly — which Meredith doesn't take particularly well — but is genuinely trying to help, and he ends up sacrificing himself in the process. Dylan loses his life as he carries the bomb out of the operating room, though Chandler returns in Season 3 alongside other deceased characters, who help Meredith find her way after she nearly drowns. Chandler is always a welcome sight, and he's the perfect addition to these truly intense episodes of "Grey's."

After getting her start in films like "Signs" and "Little Miss Sunshine" — and earning an Oscar nomination in the process — Abigail Breslin would appear on "Grey's Anatomy" in 2006 before moving on to more adult projects like "Zombieland" and "Scream Queens."

In the early Season 3 episode "Sometimes a Fantasy," Breslin appears as Megan Clover, a strange girl with a bizarre history of injuries who's living with a foster family. Though Karev, who's tasked with caring for her, immediately suspects that her parents are abusive, Megan is quick to exonerate them, saying that they're the nicest parents she's ever had ... and that she has super powers. As it turns out, Megan has an insanely high tolerance for pain and is constantly challenging friends to injure her, leading to a sustained stomach injury. The whole plotline is pretty crazy, but Breslin, even at a young age, pulls the arc off with extreme ease.

A few stars featured in "Birds of Prey," including Ella Jay Basco, showed up on "Grey's Anatomy," but we're here to give props to Black Canary herself – the one and only Jurnee Smollett – who had a huge arc to close out the series' fifth season. As Dr. Derek Shepherd (Dempsey) and Meredith suffer through a clinical trial to cure a rare brain tumor that results in several fatalities, they're just about ready to give up before they meet Beth (Smollett), a girl suffering from the tumor who's on the brink of death.

Though Derek is ready to give up, Meredith pulls some strings so that Beth will be their final patient before the trial ends. And against all odds, she makes it through the surgery, and her tumor even shrinks, making the entire endeavor worth it. Smollett is best known these days for her work in movies like "Prey" and shows like "Lovecraft Country," but back in Season 5 of "Grey's," her two episode turn as Beth — who's hopelessly in love with a fellow patient in the clinical trial — is unforgettable.

You probably know singer, songwriter, and actor Leslie Odom Jr. from his Tony Award-winning turn as Aaron Burr in the original cast of "Hamilton" or his Oscar-nominated role as singer Sam Cooke in 2020's "One Night in Miami." But back in the day, he appeared on a vital episode of "Grey's Anatomy," right alongside actor Carl Lumbly (of "Alias" and "The Falcon and the Winter Soldier").

In Season 5's "There's No 'I' In Team," Odom Jr. appears alongside Lumbly and several other guest stars — including future "Scandal" regular George Newbern — as one of a dozen patients participating in a "domino surgery," where some patients donate kidneys and others in need receive them. Odom Jr.'s P.J. Walling is a pretty unwilling participant, due in large part to a difficult relationship with his father, Kurt (Lumbly). But when Kurt gets sicker even after he receives a kidney, P.J. must grapple with his dad's death. Odom Jr. is a dynamic, multi-talented performer, and his turn on "Grey's" just proves he's been amazing for years.

If you're a fan of "Arrested Development" and "Grey's" alike, when Mae Whitman appeared in a Season 3 episode, you may have asked yourself, "Her?" Whitman, who's known for everything from "Scott Pilgrim vs. the World" to "Parenthood" to "Good Girls," appears on "Grey's Anatomy" as Heather Douglas, an angry young girl who suffers from a debilitating spinal deformation and who's been told her condition is impossible to treat.

However, when orthopedic surgeon Dr. Callie Torres (Sara Ramírez) realizes there is a treatment that can help Heather, things seem hopeful ... until Heather and her mother realize they can't afford the outrageously expensive surgery. At the last minute, Dr. Izzie Stevens (Heigl), who recently came into an extraordinary amount of money, steps in and secretly pays for the surgery. Whitman spent years playing angry teens to perfection, and Heather is yet another role that shows her incredible talent.

Fans of Ryan Murphy's high school acapella series "Glee" likely remember Matthew Morrison as the lovable, passionate teacher Will Schuester, which makes his turn on "Grey's" all the more chilling. Throughout the series, Dr. Jo Wilson (Camilla Luddington) slowly reveals tidbits about her past, including that she was homeless as a teenager and lived in her car, and finally, that she was once married to a man who abused her and knew her as Brooke. To escape him, she changed her name and ran away ... but eventually, Dr. Paul Stadler (Morrison) shows up in Seattle, hoping to get officially divorced so that he can marry another woman (who is another victim of his abuse).

Introduced in Season 13 when Jo's boyfriend Alex sees him at a convention, Morrison's Paul seems sweet at first, but when he returns for a two-episode arc in Season 14 — "1-800-799-7233" and "Personal Jesus" — viewers realize exactly why Jo ran away. Morrison usually sticks to cheerful musical theater projects, and his (doomed) performance as Paul is a frightening but enthralling change of pace for the actor.

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There are plenty of outlandish ailments on "Grey's Anatomy," but Seth Green's two-episode arc has one of the craziest cases in the show's history. Green, who you probably know from everything from "Robot Chicken" to "Buffy the Vampire Slayer," has been working in Hollywood since he was a young kid, and he's become one of the most recognizable faces in the industry during his career. And he plays a huge role during two Season 4 episodes of "Grey's Anatomy."

After Green's Nick Hanscom undergoes radical surgery to remove a tumor in his neck, he's on his way to recovery ... except that there's an extremely fragile flap of skin between his carotid artery — one of the biggest bleeders in the human body — and the outside world. As a result, resident Dr. Lexie Grey (Chyler Leigh) is tasked with watching him, and the two form a bond immediately, leaving Lexie devastated when Nick starts to bleed out. Though she does everything she can, Lexie loses Nick, but Green's turn on "Grey's" is one of the most memorable guest appearances on the show.

There's no argument amongst "Grey's" fans that Derek Shepherd is the love of Meredith Grey's life, but after he tragically dies in a car accident in Season 11, she realizes that she has to start dating again. After working with a patient who just so happens to be a matchmaker, Meredith reluctantly goes on a blind date, only to discover that the John she meets for lunch is actually meant to meet someone else. However, when Meredith and John — played by Josh Radnor — really hit it off, they ditch their dates entirely.

Of course, Radnor is best known for another role where he plays a man looking for love in all the wrong places — Ted Mosby, the problematic protagonist of "How I Met Your Mother." Though his "Grey's Anatomy" character seems, at first, like he could be a great match for Meredith, he ruins the date by telling her he finds single moms "desperate" (unaware that Meredith is a single mother of three). In classic Mosby fashion, John botches the date, and Meredith walks away, but Radnor's appearance feels like an amazing wink to fans of "Grey's" and "HIMYM" alike.