7 Best Big Bang Theory Characters That Only Appear in One Episode

One of the most popular sitcoms was The Big Bang Theory, which first aired in 2007, ran for 12 seasons, and even had a spinoff (with another one on the way), all while getting great ratings on CBS. Over the years, the show racked up more than fifty Emmy nominations and won several awards for the cast. But to make that happen, it wasn’t just about having a good story for each episode and a solid main cast. The characters also needed their backstories and key relationships to make the plot come together perfectly. This is where not just the secondary cast, but also those one-episode cameo appearances, come into play.

Many of the characters who appeared in The Big Bang Theory only for a cameo helped add depth to key details that were crucial in the broader context. How could Leonard and Penny become a couple without a little nudge from another character? How do you help Sheldon and Leonard reconcile after a fight and prevent their friendship from falling apart? These are just a few of the reasons why major guest appearances played a key role in the overall development of the show. But among all the cameos, which ones had the biggest impact?

Theodore (Christopher Lloyd)

In the episode “The Property Division Collision” from Season 10, the legendary Christopher Lloyd makes an appearance as Theodore, a drifter who ends up renting Sheldon’s old room after he moves in with his girlfriend Amy. This happens because Sheldon and Leonard can’t agree on who gets to keep the shared items in the apartment, which is now Leonard and Penny’s. Their disagreement escalates, leading to a fight between the two best friends, and that’s when Theodore settles in – much to the displeasure of Leonard and Penny. However, it’s Theodore who ultimately helps resolve the conflict and get them back on track.

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Theodore, with his strange and mysterious demeanor, quickly points out that the fight between Sheldon and Leonard is happening because of the love and affection they have for each other. What makes him so memorable is that, despite his oddities, he carries the wisdom of an older man. His unique perspective helps the two friends understand the root of their conflict, leading to their reconciliation.

David Underhill (Michael Trucco)

In Season 2’s “The Bath Item Gift Hypothesis”, Michael Trucco plays David Underhill, an award-winning physicist who seeks Leonard’s help with a research project. However, David quickly becomes a complication in Leonard’s romance with Penny. She is drawn to David’s “bad boy” charm and more outgoing personality compared to the other scientists she knows. She ends up agreeing to all of his requests, even though she refuses the same ones when they come from Leonard.

David proves to be a key figure by acting as a catalyst for the development of Leonard and Penny’s romance. His presence brings out Leonard’s insecurities and creates tension between the couple. Also, David helps Penny realize that “perfect” guys like him aren’t necessarily ideal in the long run.

Mark Hamill (Himself)

In “The Bow Tie Asymmetry” from Season 11, Mark Hamill delivers one of the most unforgettable appearances on The Big Bang Theory. From the start, it’s clear how much the main group of friends adores Star Wars and his iconic character, Luke Skywalker. Hamill appears as himself on the eve of Sheldon and Amy’s wedding, after Howard finds a lost dog that turns out to belong to the actor. When he shows up at Howard’s house to retrieve his pet, Howard manages to convince him to officiate his friend’s wedding, much to the excitement of the group.

In this case, the cameo is not only a gift for the characters of the show but for the fans. It also marks a significant milestone in Sheldon’s life, as his wedding to Amy is a major turning point in his character’s development.

Dr. Robert Wolcott (Peter MacNicol)

In “The Reclusive Potential” from season 11, Peter MacNicol plays Dr. Robert Wolcott, a scientist and Sheldon’s pen pal. Sheldon, along with Leonard, Howard, and Raj, heads to his cabin in the mountains to get his help with one of their research projects. Robert is a highly accomplished guy, but he’s also super paranoid and has some weird habits, which makes Sheldon think that he could achieve great things in life by being just like him.

The cameo is a perfect example of the lunatic genius stereotype, but with a funny twist. Of course, Sheldon is the most eccentric character on The Big Bang Theory, and it’s his quirky personality that makes him a fan favorite. However, when you compare him to someone even more bizarre, it takes the humor to a whole new level, making the episode even more hilarious.

Stan Lee (Himself)

In Season 3’s “The Excelsior Acquisition”, the spotlight is on Stan Lee, a legendary figure for the geek audience and a respected icon for the characters of the sitcom. In the episode, he is in town to sign comic books at Stuart’s comic book store. The problem arises when Sheldon can’t make it because he has to attend court for a traffic ticket he got while with Penny. He blames her for the situation, but to make it up to him, Penny tracks down Lee’s address and takes Sheldon to his house.

The big twist is that Lee doesn’t come across as a particularly happy person, especially when he unexpectedly runs into a fan at his doorstep. However, in the end, Sheldon is far from disappointed – in fact, he’s thrilled to receive a signed restraining order from the legendary Marvel icon. Despite his grumpy persona, Stan Lee still manages to shine in his cameo, making the episode one of the most memorable in the show’s history.

Alicia (Valerie Azlynn)

In the episode “The Dead Hooker Juxtaposition” from Season 2, Valerie Azlynn plays Alicia, a more successful aspiring actress who has a falling out with Penny, her neighbor. Alicia essentially becomes a kind of rival to Penny, not only because she has the career Penny has always dreamed of but also because she uses her charm to get the attention of Leonard, Howard, and Raj. This leads to a nasty confrontation between the two women.

Alicia’s role, however, is crucial because throughout the episode, she serves as a catalyst for Penny to stand up for herself and her friends. By challenging Penny’s position as the center of attention, Alicia helps push her personal development, since at the beginning of the sitcom, she was the only consistent female figure.

Mrs. Latham (Jessica Walter)

In Season 4’s “The Benefactor Factor”, Jessica Walter plays Mrs. Latham, one of the major donors at a Caltech fundraiser. She develops a huge crush on Leonard, which makes him uncomfortable. However, he believes that by reciprocating, he can help with the fundraising, so he reluctantly gets involved with her. In the end, Leonard finds out that she will still donate the money, regardless of whether they continue their involvement or not.

In general, Mrs. Latham’s actions have a ripple effect on everyone, as her behavior is petty and authoritarian. Even Howard steps out of his comfort zone because of her. She stands out as one of the most memorable cameo characters due to her role and development in the storyline. It’s no surprise that this episode earned Johnny Galecki an Emmy nomination.

The Big Bang Theory is available to stream on Max.