Whatever you think about The Big Bang Theory and its questionable setting and quality decline, there have been a few great characters who have only shown up once. Sometimes they appear in a minor role and help to form the storyline, while occasionally a celebrity guest pops by with an impressive couple of minutes.
We’ve taken a look at ten of the best one-off characters and unearthed their best quote(s) for your reading pleasure.
Jesse
Josh Peck (of Drake And Josh fame) portrays the sleazy owner of Capitol Comics, the main rival of Stuart’s well-loved but under-stocked comic book store. He appears in ‘The Occupation Recalibration’ in season 7 and uses his screen time to really lay into Stuart. It’s rough but undeniably funny. ‘Look how grey you’ve gotten’ he says a couple of seconds after appearing on-screen. When Stuart explains that his hair is the same color as always, Jesse says ‘No, I was talking about your skin.' Harsh, but fair.
Mark Hamill
Known for his iconic portrayal of Luke Skywalker in the original Star Wars trilogy and the much more recent Star Wars sequel trilogy, Mark Hamill was always destined to appear in The Big Bang Theory. When he finally does, it’s to officiate Sheldon and Amy’s wedding. Impressive.
The boys are all particularly excited (especially Howard, when Mark arrives at his door unexpectedly), but he delivers his funniest and most important line during the ceremony: ‘By the power vested in me by evenyoucanperformweddings.com, I now pronounce you husband and wife.'
Sandy
It’s hard to hear Yeardley Smith speaking without hearing the voice of Lisa Simpson, so when she makes an appearance as Sandy, the clerk at a job center when Sheldon is trying to find a menial job, it's particularly hard not to picture a spiky yellow head. She manages to deliver some impressive retorts to Sheldon’s arrogant anger during their meeting. When he suggests her job is menial, she fires back with ‘Why thank you for noticing, I’m menial employee of the month’, and when he calls her out for pretend typing, she responds ‘I didn’t really have to.' Her brilliant one-off appearance ends with her calling for security to escort Sheldon out.
Mikayla
You might recognize Mikayla from Prison Break, where Jodie Lynn O’Keefe plays the scheming, deceptive Gretchen Morgen. In The Big Bang Theory, she couldn’t be further (well... sort of) from that character, as she takes on the guise of a prostitute paid to provide Howard with the Jewish girlfriend experience.
When she approaches Howard she has a few Jewish stereotypes up her sleep, immediately grabbing his attention with ‘Boy, would it kill them to put out a nice brisket?’ and then introducing herself as Esther Rosenblatt.
Theodore
Considering the Big Bang Theory creators managed to land a cameo appearance from Back To The Future actor Christopher Lloyd himself, the role they put him in was certainly an interesting one. He is a creepy old man that rents a room in Sheldon’s apartment during the episode ‘The Property Division Collision’, but ends up giving some pretty good advice about Sheldon’s fight with Leonard. Even though the show doesn’t go down the one-liner route very often, his first line is a classic. When Leonard asks, ‘Can I help you?’ he responds ‘I don’t think so, but you’re sweet for asking.'
Christy Vanderbel
Appearing only in ‘The Dumpling Paradox’, Christy is introduced as one of Penny’s former friends. She causes more than her fair share of trouble, ending up sleeping with Howard (who was yet to be tamed by Bernadette) and exploiting his desperation by getting him to take her shopping.
Even though she isn’t the nicest character the show has ever introduced us to, she does give us one of the most iconic lines in its history, much to everyone else’s confusion and disdain: ‘My first Jew!’
Sebastian
Sebastian is a particularly interesting one-off character. He is played by Steven Yeun (Glenn in The Walking Dead) and appears only once, in a flashback to when Leonard moves in with Sheldon.
He utters one line, the relatively ominous ‘run fast, run far’ and leaves Leonard to find the words ‘die Sheldon die’ scrawled in red paint on his future bedroom. Considering he only had one line, it seems pretty conclusive that Sebastian was not a fan of Sheldon’s shortcomings.
Stan Lee
Not one to shy away from cameos in his own Marvel franchise, Stan Lee made his own Big Bang Theory appearance in ‘The Excelsior Acquisition’, appearing at the comic book store for a signing. Having been mentioned in a multitude of episodes before this, the boys were all obviously very excited to meet him, even if Sheldon missed the opportunity as he was in court at the time. When Sheldon and Penny turn up at his house uninvited, he gives us the sarcasm laden line, ‘Why don’t you just come on in and watch the Lakers game with me?’ which of course, Sheldon attempts to accept this offer jubilantly.
Toby Loobenfield
In quite a meta role, Toby Loobenfield is an actor cast by Sheldon to play his drug-addicted cousin Leopold (who doesn’t exist) in order to convince Penny his excuse to not see her perform in Rent was legit. His performance is surprisingly excellent as Leopold, bursting into a monologue that tries to justify his character’s struggle: ‘His only companions mongrel dogs and malarial mosquitoes.’ His character just gets better when he reverts to Toby and still won’t leave. We see him become attached to Penny and the episode ends with him leaning on Penny’s laughing shoulder. What a great guy.
James Earl Jones
The voice of Darth Vader is known for his unexpectedly bubbly, fun-loving spirit and his guest appearance in ‘The Convention Conundrum’ might well be the most perfectly executed cameo the show has ever had, potentially other than Carrie Fisher who appears in the very same episode.
Sheldon and James Earl Jones end up having a day out together, getting ice cream, going to a carnival, a strip club and Carrie Fisher's house, and finally ending up in a sauna. It’s hard to pick a favorite line from this golden episode, but when the booming tones of Darth Vader ring out the words ‘Let me guess, you like Star Wars?’ it was obvious we were in for a treat.