10 Unforgettable Celeb Cameos on The Big Bang Theory

1. Stan Lee (Season 3, Episode 16 The Excelsior Acquisition)

When Penny tells Sheldon she got him an autograph from none other than Stan Lee, the comic book god himself, Sheldon is over the moon – until he realizes he missed the signing due to a court appearance for a traffic violation. Penny has the inside scoop on where Stan Lee's private signing is taking place. Sheldon and Penny show up at Stan Lee's house uninvited, and Sheldon actually meets him – but not the way he planned. He ends up getting a restraining order from Stan Lee himself. Classic Sheldon!

2. Wil Wheaton (Multiple Episodes)

The infamous Wil Wheaton rivalry. Initially appearing in Season 3's The Creepy Candy Coating Corollary, Wil Wheaton plays himself and is Sheldon's sworn enemy. Why? Because Wheaton didn't show up at a fan event Sheldon attended as a child. In this particular episode, they face off in a Mystic Warlords of Ka'a card game tournament. Sheldon loses after Wheaton lies about his grandma dying to win sympathy points. Over time, Wheaton becomes a recurring character and even becomes friends with Sheldon.

3. George Takei (Season 4, Episode 4 The Hot Troll Deviation)

In a hilarious twist, George Takei appears as himself – but in Howard's fantasy. After getting back with his ex-girlfriend Bernadette, Howard has a dream where Katee Sackhoff (from Battlestar Galactica) and George Takei offer relationship advice. What's funny is that both George and Katee question why they are in Howard's fantasy together.

4. Leonard Nimoy (Season 5, Episode 20 The Transporter Malfunction)

Leonard Nimoy, the OG Spock, lends his voice to a Spock action figure in Sheldon's dream. Sheldon gets the mint-condition action figure as a gift but can't resist opening it. Dream Spock then convinces Sheldon to play with the toy, leading to Sheldon breaking it. While you never see Nimoy in person, his voice adds a layer of authenticity that's irresistible.

5. Stephen Hawking (Season 5, Episode 21 The Hawking Excitation)

Stephen Hawking himself graces the halls of Caltech, and Howard gets the job of maintaining his wheelchair. Sheldon has been eager to meet Hawking, and Howard agrees to introduce them – but only if Sheldon agrees to do some demeaning tasks. Sheldon actually does everything from polishing belt buckles to applying lotion on Howard's back. When he finally meets Stephen Hawking, he shows him a paper on the Higgs boson, only to be embarrassed by a mathematical error Hawking points out. It's rare to see Sheldon embarrassed, but if anyone's gonna do it, it's Stephen Hawking!

6. Bill Nye (Season 7, Episode 7 The Proton Displacement)

Bill Nye the Science Guy comes into play when Sheldon finds out that his childhood hero, Professor Proton (played by Bob Newhart), is hanging out with Leonard instead of him. Feeling betrayed, Sheldon befriends Bill Nye to make Proton jealous. Unfortunately for Sheldon, Bill Nye ends up ditching him, and he finds himself with yet another restraining order.

7. James Earl Jones (Season 7, Episode 14 The Convention Conundrum)

After failing to get Comic-Con tickets, Sheldon decides to create his own comic book convention and starts by trying to invite James Earl Jones. Unlike his other celeb encounters, this one goes spectacularly well! Sheldon finds out where Jones is dining, joins him for dinner, and they end up having an epic night: eating ice cream, riding a Ferris wheel, and even ding-dong ditching Carrie Fisher!

8. Bob Newhart as Professor Proton (Multiple Episodes)

Comedy legend Bob Newhart plays Arthur Jeffries, also known as Professor Proton, Sheldon and Leonard's childhood science hero. He first appears in Season 6, hired by Sheldon and Leonard to perform for them. Initially skeptical, he later becomes a sort of mentor to Sheldon. He also appears as a Force ghost in Sheldon's dreams in later seasons, offering him advice on various problems.

9. Howie Mandel (Season 6, Episode 4 The Re-Entry Minimization)

Remember when Howard went to space? Well, on his way home, he ends up sharing a plane with Howie Mandel. What should've been a special moment turns awkward when the crowd starts chanting "Howie, Howie!" and Howard mistakes it for his own welcoming as a returning astronaut.

10. LeVar Burton (Multiple Episodes)

After an ill-advised tweet from Sheldon, LeVar Burton shows up unannounced at Sheldon's party in Season 4 only to flee when he's overwhelmed by the party members look and behavior. He makes a second appearance in Season 6, attending Sheldon and Amy's "Fun with Flags" episode.