Joss Whedon

Buffy the Vampire Slayer: Bewitched, Bothered, and Bewildered

With his goofy likability and acknowledged role as a Zeppo, Xander makes for good comedy, no matter how much "field time" he’s clocked. After Cordelia breaks up with Xander on Valentine’s Day, Xander gets his witchy friend Amy to cast a spell to make Cordelia fall madly in love with him. Of course, it backfires spectacularly. Xander rapidly finds himself the object of desire of every woman—alive or dead—in Sunnydale. And they will stop at nothing to get their hands on him.

Angel: Smile Time

Angel is a vampire with a soul, and he stoically fights whatever demonic scourge comes his way. The watchword here is "stoic." Angel was famed for his serious, even forbidding, demeanor. So when he came afoul of a plot to steal the life forces of children, the show reached the apex of absurdity when Angel was turned into a Muppet-style version of himself. We howled with laughter at his removable nose, his bouncy walk and the way the other characters reacted to his adorable felt body. And just when you think the episode couldn’t get any funnier, puppet-Angel goes through, um, some other transformations. Brilliant.

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http://blastr.com/2010/11/10-funny-episodes-of-classic-sci-fi-tv-dramas.php