The Big Bang Theory's cast of scientists and engineers all had a passion for famous professionals in their field, as well as the actors and creators of the science fiction franchises that they loved. Many of the character's role models and fandoms were true to the real world, making the show uniquely able to bring in relevant guest stars to either play original characters or cameo as themselves.
Every guest star that joined the show was a pleasure for audiences to see, but over the seasons, there were a few that stood out. These stars have achieved much in their careers, and it was exciting to see them step away from their normal jobs to interact with Sheldon and the gang.
Leonard Nimoy - Season 2, Episode 11
Leonard Nimoy is the actor that played Mr. Spock in the original Star Trek series, even reprising his role in the more recent movies starring Chris Pine.
He did not appear on screen in his guest episode on The Big Bang Theory. Instead, he gave his voice to a Spock action figure belonging to Sheldon. The action figure shames Sheldon for swapping out a toy that he had broken for an intact one belonging to Leonard, leading him to do the right thing. Sheldon often references Nimoy as a favorite actor and hero, and eventually, it is revealed that Sheldon has a restraining order from the star that he prizes and keeps framed on his wall.
Stan Lee - Season 3, Episode 16
Stan Lee is the legend responsible for many of the Marvel stories fans know and love. He is the brain behind characters like Spider-Man, Iron Man, Thor, The Hulk, and Black Panther. It goes without saying that he is basically a god in the comic world.
Because of this, Sheldon is distraught when he misses his chance to meet Lee at their local comic book shop. Instead, he and Penny decide to just show up on his doorstep and ask for an autograph. Stan Lee did a great job acting angry at their rude appearance. This should have been an embarrassing moment for Sheldon Cooper, but instead, he was just excited to have met his hero and get his autograph (on a restraining order.)
Neil DeGrasse Tyson - Season 4, Episode 7
Neil DeGrasse Tyson is an astrophysicist, which is Raj's career on the show. Not only has Tyson contributed greatly to the scientific community, but his television shows like Cosmos and A Spacetime Odyssey have brought the passion for science to audiences of all ages.
In The Big Bang Theory, Tyson portrays himself, immediately hitting it off with Raj, and fans would expect him, as a scientist, to get along with Sheldon and Leonard as well. However, in classic Sheldon fashion, Tyson is taken aback by Sheldon's direct manner of speaking and reacts defensively to being accused of removing Pluto's status as a planet.
Stephen Hawking - Season 5, Episode 5
Stephen Hawking is a theoretical physicist and one of the greatest minds of the age, if not in history. At the time of his death, he was the director of research at the Centre for Theoretical Cosmology at the University of Cambridge.
Despite his importance in the world of science, Hawking took time out to portray himself in The Big Bang Theory for multiple episodes, starting in Season 5 Episode 5 when he and Sheldon meet while playing Words With Friends online. After his death, the show paid him one last tribute by having Sheldon and Amy receive a final gift from him for their wedding, an emotional moment that had The Big Bang Theory audiences crying.
Bill Nye - Season 7, Episode 7
Bill Nye is best known for his education series for kids, Bill Nye the Science Guy, which became a beloved addition to any kid's classroom. Nye, who is an engineer by profession, has been able to contribute not only to the education of young people but also designed features of the Mars rover.
He appears as himself in season seven of The Big Bang Theory, butting heads with Sheldon's childhood hero Professor Proton, who ran a similar (but fictional) science show for children.
James Earl Jones - Season 7, Episode 14
James Earl Jones is an actor who is best known for lending his voice to Darth Vader. His deep rumbling voice is unmistakable, with his lines being some of the most quoted from the hugely popular Star Wars films.
Sheldon spots James Earl Jones at a restaurant and approaches him. The two end up becoming fast friends and go on an evening-long adventure. They sing karaoke, steam in a steam room, and even prank Carrie Fisher by ringing her doorbell and running away.
Carrie Fisher - Season 7, Episode 14
Carrie Fisher starred along with James Earl Jones in the original Star Wars trilogy. Her role as Princess Leia earned her worldwide recognition and four Saturn Award nominations. She was also known for her feisty personality, never stepping back from saying whatever she felt.
This quality was perfectly incorporated in her role on The Big Bang Theory when she chases Sheldon and Jones from her house with a baseball bat. Oddly enough, Fisher and James met for the first time during this cameo, since Jones never came to the Star Wars set.
Elon Musk - Season 9, Episode 9
Elon Musk is the billionaire genius behind companies like SpaceX, Tesla Motors, and SolarCity. According to Forbes, Musk is the wealthiest person on earth, with a net worth of $15.2 Billion.
Despite his status and very busy schedule, Musk still took the time to appear in The Big Bang Theory as himself, surprising fellow engineer, Howard, by working along with him in a soup kitchen. Howard spends a little time boasting of his achievements and trying to prove himself to be the smartest character on The Big Bang Theory, but the two eventually make a connection, with Musk inviting Howard to keep in touch.
Kathy Bates - Season 11, Episode 24
Kathy Bates is the legendary actress who has earned the Academy Award for Best Actress for her role as Annie Wilkes in Misery. She is also known for her roles in Fried Green Tomatoes and Titanic.
Kathy is one of the few big guest stars to not portray themselves in The Big Bang Theory. Instead, she surprised viewers by appearing as Amy's mother. Mrs. Fowler is hilariously controlling of her husband and daughter, often making critical comments about Amy's life and friends. Kathy delivers her lines expertly, keeping audiences laughing.
Mark Hamill - Season 11, Episode 24
Mark Hamill is known for playing Luke in the original Star Wars trilogy and reprising his role in the recent sequels. He also does a great deal of voice acting, most notably as The Joker in Batman: The Animated Series.
In the series finale, Howard manages to get Mark Hamill (playing himself) to agree to officiate Sheldon and Amy's wedding. Hamill battles with Wil Wheaton, who was originally supposed to officiate. The ceremony went well, with Hamill giving a touching speech, and breaking down into tears over the beautiful vows.