17 Memorable Guest Appearances on The Big Bang Theory

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These special guests appeared on The Big Bang Theory as themselves for some incredibly hilarious moments. Check them out!

1. Leonard Nimoy

Leonard Nimoy
We begin with the recently deceased cultural icon, Leonard Nimoy. In Season 5, the Star Trek star acted as the voice of Sheldon's rather opinionated Mr. Spock action figure.

2. Summer Glau

Summer Glau
In Season 2, Leonard, Howard, and Raj spot Summer Glau (Firefly, Serenity, The Terminator) on a train, and promptly all make fools of themselves.

3. Charlie Sheen

Charlie Sheen
Charlie Sheen makes an appearance in Season 2, when he and Raj have a brief encounter at The Cheesecake Factory.

4. Stan Lee

Stan Lee
In Season 3, Sheldon manages to get a restraining order against him by Stan Lee.

5. Wil Wheaton

Wil Wheaton
Best known for his role on Star Trek: The Next Generation, Wil Wheaton has made more than a few appearances, most of which involve him antagonizing Sheldon. He made his first appearance in Season 3.

6. Neil Degrasse Tyson

Neil Degrasse Tyson
Neil Degrasse Tyson, astrophysicist and host of the show, Cosmos, appeared in Season 4.

7. Katee Sackhoff

Katee Sackhoff
Best known for her role on Battlestar Galactica, Katee Sackoff appears in Howard's fantasies in Season 3.

8. George Takei

George Takei
Star Trek's George Takei appears in Season 3. In a fantasy that begins with aforementioned actress, Katee Sackoff, George Takei makes an accidental appearance (along with Bernadette).

9. LeVar Burton

LeVar Burton
Star Trek: The Next Generation's LeVar Burton is also known for hosting "Reading Rainbow." He has made a few appearances, the first of which was in Season 4. He's even taken part in "Fun with Flags."

10. Stephen Hawking

Stephen Hawking
Scientist Stephen Hawking has appeared a few times, but Sheldon first had the chance to meet his idol in Season 5.

11. Brent Spiner

Brent Spiner
Best known for his role on Star Trek: The Next Generation, Brent Spiner appears in Season 5 long enough to ruin Sheldon's action figure.

12. Buzz Aldrin

Buzz Aldrin
Astronaut Buzz Aldrin appears in Season 6, giving out Halloween Candy and bragging about walking on the moon.

13. Howie Mandell

Howie Mandell
In Season 6, Howie Mandell steals Howard's spotlight when he returns from space.

14. Bill Nye

Bill Nye
Bill Nye appeared in Season 7 as a rival to "Professor Proton," who was played by another special guest, Bob Newhart.

15. James Earl Jones

James Earl Jones
In Season 7, Sheldon gets to hang out with James Earl Jones. Included in their activities are ice cream, a ferris wheel ride, karaoke, and even playing a prank. Which brings me to...

16. Carrie Fisher

Carrie Fisher
Also appearing in Season 7, Carrie Fisher is the victim (and that's a strong word) of a prank by Sheldon and James Earl Jones.

17. Nathan Fillion

Nathan Fillion
In Season 8, Raj and Leonard try to decide if they man they run into a deli is actually Firefly's Nathan Fillion. Of course, you might also recognize Fillion from a hit show called Castle.

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