The Big Bang Theory Actors You May Not Know Passed Away

There are many advantages to growing up. You can own a house and drive a car — and you can pass your pop culture inspirations down to the younger generation. That's precisely what "The Big Bang Theory" did, as the show featured enough likeable characters, references, and guest stars to fill a "Star Trek" convention. In fact, many of the cameos filed in from all corners of pop culture, from movies to comic books and everything in between — including "Star Trek."

However, for every upside, there is a downside, and the biggest downside of growing up is that you eventually see the people you know and love, be they family or actors, pass away. "The Big Bang Theory" featured many thespians crucial to the current face of pop culture over the show's 12 seasons, and not all of them lived to see the finale. The following "The Big Bang Theory" actors are no longer with us.

A major ingredient in the comedy of "The Big Bang Theory" is its reliance (and twisting) of common nerd clichés. For example, Sheldon Cooper (Jim Parsons) is an egocentric introvert with Vulcan-like emotions, while Howard Wolowitz (Simon Helberg) is a geek who lives with his mother, Mrs. Wolowitz, who still treats him like a child. In the Season 8 episode "The Comic Book Store Regeneration," Howard reveals that his mother died in her sleep. Normally, actors are written out in such a way because they leave shows for other projects, but in Mrs. Wolowitz's case, she died both in the show and in real life.

On the morning of Tuesday, November 11, 2014, Carol Ann Susi, the voice of Mrs. Wolowitz — the character never appeared onscreen as a running gag — died of cancer (via The Hollywood Reporter). She was 62. At the time, the writers were unsure how Susi's death would impact the show, but she was officially written out of the series in "The Comic Book Store Regeneration," when the characters mourned her death. According to another Hollywood Reporter article, this storyline was "one of two options" the producers wanted to explore. The article implied that the second option was asking Melissa Rauch (who played Bernadette Rostenkowski-Wolowitz on the show) to replace Susi with her "spot-on impression."

Because "The Big Bang Theory" was on the air for 12 years, it ran through numerous guest actors, many of whom you might not recognize. One obscure name was Jane Galloway Heitz, who appeared in the Season 2 episode "The Friendship Algorithm" as the minor character Mildred. However, Heitz had a lengthy career playing minor characters in shows such as "ER," "Grey's Anatomy," "Monk," and "Glee," and before all that, she appeared in movies such as David Lynch's "The Straight Story." Before Heitz started acting, she was a casting agent (via The Hollywood Reporter), but in 1997, Heitz sold her agency to pursue a career as an actress.

According to The Hollywood Reporter, on November 13, 2019, Heitz died due to congestive heart failure. Her husband, TV producer Bill Heitz, died in 2002. Heitz was survived by her daughter, Amie Richardson, as well as her grandchildren Jack, Claire, and William.

Since the main characters of Sheldon Cooper, Leonard Hofstadter (Johnny Galecki), Howard Wolowitz, and Rajesh Koothrappali (Kunal Nayyar) work at the California Institute of Technology, they aren't just into science fiction; they also love science fact and the champions of science. Famous faces within the scientific community, such as Neil deGrasse Tyson, Bill Nye, and Stephen Hawking, popped in once in a while. Actually, Hawking popped in more than once.

Hawking appeared in multiple episodes throughout the series' run, including "The Hawking Excitation," "The Extract Obliteration," and "The Celebration Experimentation." He became fast friends with Sheldon. Moreover, he told Sheldon to turn the finger of Amy Farrah Fowler (Mayim Bialik) into Saturn and "put a ring on it." Hawking was once considered the smartest man on the planet, so you couldn't ask for better advice.

On March 14, 2018, Hawking died peacefully in his sleep at the age of 76. According to the article, he was diagnosed with a rare motor neuron disease at the age of 22, and doctors predicted he only had a few years to live. Hawking defied the odds, but he lived most of his life in a wheelchair and used a voice synthesizer. Who can say how many more "The Big Bang Theory" episodes would have guest-starred Hawking had he not passed away? Given his fictional incarnation's relationship with Sheldon, Hawking might have shown up for the series finale.

When the main cast of "The Big Bang Theory" aren't eating in the California Institute of Technology's cafeteria or crashing in Sheldon and Leonard's living room, they are perusing the latest offerings from the local comic store. As such, comics play a big part of their lives and the show, so it would only make sense for the king of comics, Stan Lee, to appear in "The Big Bang Theory."

Stan Lee cameoed in the episode "The Excelsior Acquisition," and unlike most guest stars, Lee's show incarnation didn't get along well with Sheldon. In that episode, Sheldon goes to court because he ran a red light while driving Penny (Kaley Cuoco) to the hospital in "The Adhesive Duck Deficiency." The court date prevents Sheldon from meeting Lee at the comic store, and since Penny feels bad — and knows where Lee lives — the two drop by his house uninvited. As a result, Lee files and signs a restraining order against Sheldon, who hangs it on the wall. Stan Lee's signature is still Stan Lee's signature, no matter what it's on.

In 2018, Lee passed away due to heart failure. He was 95 years old.

A common trope is parents hiring entertainment for their kids' birthday parties. Sometimes they employ clowns; other times they bring in someone dressed as Spider-Man. Sheldon Cooper can one-up all those kids because he got to see the real Batman for his birthday, and he only had to wait 30 years.

In the episode "The Celebration Experimentation," Leonard, Raj, and Howard are trying to figure out what to get Sheldon for his birthday present. Since Sheldon was devastated Batman didn't show up for his sixth birthday, his friends decide to invite one of the actors who portrayed Batman, Adam West. And, he isn't that hard to find because the local comic store owner, Stuart Bloom (Kevin Sussman), has West's contact information. While ferrying West to Sheldon's birthday, Leonard, Raj, and Howard have a heated debate over who was the best Batman actor, and West has his own opinion on the matter.

Adam West died peacefully surrounded by family members in 2017 at the age of 88.

While "The Big Bang Theory" episodes cover a gamut of stories, they frequently feature two specific story beats: Sheldon and his friends geek out when they meet a pop culture icon, and you never know how (or if) they will gel. Sometimes the celebrity participates in a friendly yet heated debate; other times Sheldon and co. wrap the celebrity up in shenanigans or vice versa. If it weren't for the latter, Sheldon would have never visited Carrie Fisher.

In the episode "The Convention Conundrum," Sheldon can't get tickets to San Diego Comic-Con, so he tries to create his own comic convention instead (as one does). To start, he plans to invite his favorite "Star Wars" actor. No, not Carrie Fisher, James Earl Jones. Of course, this involves a bit of stalking, but Jones is a good sport and invites Sheldon to hang out at a carnival and do karaoke, as well as prank some neighbors with a ding-dong ditch. One of these neighbors is none other than Fisher, who runs outside with a baseball bat since Jones has constantly targeted her with that prank. Unlike Jones, Fisher's role in "The Big Bang Theory" starts and ends at being the annoyed victim of Jones' antics.

In December 2016, Fisher was on an airplane when she suffered a "massive heart attack" (via TMZ). While an emergency medical technician was onboard at the time and tended to her, by the time the plane landed, she was "unresponsive." Fisher was rushed to an intensive care unit but died days later (via CBS). She was 60 at the time.

Even though Jessica Walter didn't have the same sci-fi and comic credits as Mark Hamill and Kevin Smith when she appeared on "The Big Bang Theory," she still had a long and prolific career that would be the envy of most actors. Walter is best known as Lucille Bluth on "Arrested Development" and Malory Archer on "Archer," but she also played characters such as Fran Sinclair on "Dinosaurs." 

Walter appeared in "The Benefactor Factor" as Mrs. Latham, the titular benefactor. Mrs. Latham initially comes off as condescending, and that's because she is. She just loves making smart people feel uncomfortable (her words, not ours). As the episode goes on, Leonard does anything he can to secure funds for his department, including going on dates with Mrs. Latham. Hijinks ensue, but the audience never learns how the dates truly went — and are probably better off not knowing (hint, hint).

Jessica Walter passed away on March 24, 2021, in her sleep at the age of 80.

Out of all the sci-fi actors the main characters adore, none are referenced more often or are closer to Sheldon Cooper's heart than Leonard Nimoy. Sheldon owns a napkin signed by Nimoy, a restraining order signed by Nimoy, and a Spock action figure. Since Sheldon's heart is seemingly shaped like a Vulcan greeting, you might be surprised to hear that Nimoy never appeared on the show. But Spock did. It sounds confusing, but it's easily explained.

During the episode "The Transporter Malfunction," Penny purchases "Star Trek" transporter toys for Sheldon and Leonard, and initially, both are content to keep the toys mint-in-box. But, Sheldon's dream consciousness, taking the form of a Spock toy and borrowing Nimoy's voice, convinces Sheldon to take the transporter out of the box and play with it. Sheldon does so (because who wouldn't refuse advice from Spock) and accidentally breaks his toy, so he switches his with Leonard's under the assumption that he would never take it out of the box. Afterward, the dream Spock takes the role of Jiminy Cricket and convinces Sheldon to set things right.

On February 27, 2015, Nimoy passed away at the age of 83 due to chronic obstructive pulmonary disease. In 2014, he'd publicly announced that he had the disease and blamed his smoking habit earlier in his life.

Every young protagonist needs a mentor, and the man responsible for taking on that role in "The Big Bang Theory" was Professor Proton (Bob Newhart), albeit unwillingly. Real name Arthur Jeffries, the figure was a children's entertainer and science host who was a favorite of both Sheldon and Leonard during their youth. Somewhat grumpy and reluctant to engage with the pair when they hire him, he warms up to them eventually but is still not exactly happy to be forced to interact with Sheldon regularly.

Newhart was actually nominated for several Primetime Emmy Awards for his role as Arthur in 2014 and 2016. Before that, he landed the gong for outstanding guest actor in a comedy series in 2013 after appearing in the episode "The Proton Resurgence" — his first appearance in the series. Newhart went on to appear in several other episodes, taking his number of appearances in the sitcom to six in total, with his final on-screen credit coming in the Season 12 episode "The Planetarium Collision." He also appeared in "Young Sheldon" for several episodes, sometimes as only the voice of Professor Proton.

Newhart died on July 18, 2024, at the age of 94. A statement from his publicist Jerry Digney confirmed that he had suffered from several short illnesses before his death and that he had passed away at his home.

"The Big Bang Theory" regularly featured guest stars from the geekier side of pop culture. Among the biggest names to ever grace the CBS sitcom were a string of "Star Wars" actors. Appearing in the Season 7 episode "The Convention Conundrum" alongside original "Star Wars" trilogy alum Carrie Fisher, James Earl Jones didn't take on his classic role as the Darth Vader but instead played himself, tagging along with Sheldon on a wild night of partying after a failed trip to Comic Con. Ironically, it was the first time that Fisher and Jones shared the screen.

One of cinema's greatest icons, Jones actually got his start on television, appearing in guest roles in soap operas like "The Guiding Light" and "As the World Turns." His big-screen breakout was 1970's "The Great White Hope," playing a Black boxer who becomes the target of racism while romantically involved with a white woman. From there, Jones became known for his towering stage presence — not to mention his dulcet tones. From "Star Wars" to "Field of Dreams" and "Conan the Barbarian," his roles ran the gamut.

His "The Big Bang Theory" episode would mark one of his last appearances on-screen. Jones passed away in September 2024 at the age of 93. He will forever be remembered as Darth Vader, Mufasa from "The Lion King," and the voice of CNN, but, moreover, as one of the finest actors who ever lived.

Veteran TV character actor Ronald Hunter made his debut in a 1976 episode of the BBC show "Horizon," playing the titular Dr. Edelin in the episode "The Edelin Affair." He cemented himself as a go-to guest actor during the 1980s with appearances in smash hits like "Cagney & Lacey," "Magnum P.I.," and "Knots Landing." He didn't slow down after the decade turned over into the 1990s, showing up in even bigger TV sensations like "NYPD Blue," "Ally McBeal," and "Law & Order."

In 2008, Hunter made his one and only appearance on "The Big Bang Theory," popping up in the episode "The Peanut Reaction" (so named because Howard fakes an allergic reaction to get Leonard out of his apartment so the others can set up a surprise party for him). While shopping for a gift for Leonard in an electronics store, Sheldon ends up giving advice to several customers, including Hunter's Dan, who wants to know which kind of hard drive he should buy.

Around that same time, Hunter was showing up in episodes of "Monk," "Criminal Minds," and the memorable but short-lived "Journeyman," but he was also well-known for his work on the stage. In fact, his Broadway debut came in a production of "Richard III" alongside Hollywood legend Al Pacino. He died of heart and kidney failure complications at the age of 70 in 2013.

In "The Bozeman Reaction," an episode from Season 3 of "The Big Bang Theory," Sheldon and Leonard are gobsmacked when they become victims of an apparent burglary. Julio Oscar Mechoso plays Officer Hackett, who takes their statement. Mechoso was a veteran of TV who counted a number of top dramas among his credits, such as "Nip/Tuck," "Cold Case," and "CSI." 

Though Mechoso often turned up in single-episode roles, the actor did have some recurring parts. Most notably, he starred alongside Gabriel Luna in the action-drama "Matador," about a soccer player-turned-CIA agent, and in three episodes of the Jimmy Smits-led drama "Cane." Mechoso also starred in a sitcom before "The Big Bang Theory," leading the short-lived "Greetings from Tucson," in which he played the patriarch of a Mexican-American family dealing with the trials and tribulations of American life.

Prime time audiences might remember Mechoso from his memorable recurring role as Martin on "Coach" in the 1990s, or even his brief but memorable appearance as a disgruntled fellow tenant of Jerry's in the "Seinfeld" episode "The Kiss Hello." Mechoso died at the age of 62 in 2017 following a heart attack.

Some guest actors on "The Big Bang Theory" are globally recognized faces, like Leonard Nimoy or Stephen Hawking, who stroll on-screen to raucous cheers. Others become known to fans for their voice alone, like Travis Davis, who voiced a memorable character in the 2009 episode "The Classified Materials Turbulence." In that episode, Howard creates an advanced toilet using experimental technology designed for use on the International Space Station. Davis provided the voice for NASA's ground control operator.

Davis wasn't a major star, but he had a healthy career in TV and video games that grew out of his comedy roots. He was a member of the sketch comedy review group at ACME Comedy Theater and he later became a student member of the world-famous Groundlings — the troupe that produced such talents as Will Ferrell, Melissa McCarthy, Kristen Wiig, and Phil Hartman. On TV he appeared in episodes of "Walker, Texas Ranger," "Norm," and "Desperate Housewives," while on the big screen, he had small roles in favorites like 2002's "Slackers" and 2009's "Friday the 13th."

Some of Davis' bigger work came as a voice artist in video games, playing characters for entries in franchises like "Command and Conquer," "Ratchet & Clank," and "Medal of Honor." His role in "The Classified Materials Turbulence" was his final voice role before his passing in 2009.