The comic book creator — who famously had cameos in many of his own movies — played himself
Gates made his cameo in season 11, spending the day at Penny’s company — much to the surprise of her pals. Leonard inserts himself, though, finding Gates at his hotel and introducing himself, ruining a surprise Penny planned for him in the process. And Sheldon thinks the entire meeting is a prank, given its April 1 timing (it’s not!).
The Science Guy himself came on to the show in season 7 (and again in season 12), when Sheldon brought him in to get revenge on Professor Proton (Bob Newhart). Another restraining order ensued.
So no, he’s not a scientist, but the beloved actor appeared on six episodes of the show playing the guys’ childhood icon, Professor Proton. The role earned him three Emmy nominations and one win.
In season 6, the iconic astronaut appeared in the form of a video showing him handing out Milky Way and Mars bars on Halloween — and talking up his storied career to kids.
One of several Star Wars guests, Fisher appeared briefly in season 7, when Sheldon and his new friend James Earl Jones ding dong ditched her.
You read that right — new friends with Sheldon. The two bond over their love of Star Wars in the season 7 episode, and have dinner together before getting wrapped up in all sorts of antics.
The Tesla founder was a guest in season 9, volunteering at a soup kitchen on Thanksgiving with Howard. He later had a cameo on an episode of the Big Bang spin-off, Young Sheldon.
Luke Skywalker had a very important guest role on TBBT, serving as officiant for Sheldon and Amy’s season 11-ending wedding. He got roped into the task after Howard found his lost dog and he offered him a favor as thanks.
Onto Star Trek! Takei popped up in season 4, offering Howard some romantic advice during a fantasy sequence. (His costar Leonard Nimoy appeared in season 5, voicing his own action figure, and Nimoy’s son had a bit part in season 9).
The actor’s guest spot stretched across three episodes in seasons 4, 6 and 8, first invited over for dinner via Twitter by Sheldon. His later spots involve appearances on “Sheldon Cooper Presents: Fun with Flags” — though in his final episode, he cuts ties with Sheldon for good.
In season 4, Tyson, chummy with Raj, engaged in a war of words with Sheldon over the demotion of Pluto as a planet. He surfaced again briefly in a season 12 episode, too.
Between 2012 and 2017, physicist Hawking appeared in some form on seven episodes of the series, the first time in an episode devoted entirely to him in season 5. Following his death in 2018, the cast paid tribute to him in a special season 11 finale scene that was released online.