Robin Williams Robin Williams

What is Robin Williams' favorite genre of television? Science fiction!

"I'm a science fiction nerd," Williams tells in his celebrity Watchlist video. "I watch all of the different science fiction shows. Defiance, I watch you... Game of Thrones — big fan of Khaleesi."

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Williams, who makes his return to television this fall on CBS' The Crazy Ones, also admits to being a big fan of his co-star Sarah Michelle Gellar's work. Which role of hers was his favorite? Find out below:

The Crazy Ones premieres Thursday, Sept. 26 at 9/8c on CBS.

(Full disclosure: is owned by CBS.)