1 of 10
The Oscar-nominated actress guest-starred in the season 5 episode "Family," where she plays Tara's nasty cousin Beth.
2 of 10
The Harold and Kumar star plays a bro-y UC Sunnydale student in the season 4 episode "Beer Bad," in which the beer he and Buffy are drinking has been put under a spell by a bitter bar owner.
3 of 10
While he didn't appear in the series, he did give a glorious performance as a teen basketball player in the 1992 classic, yet misunderstood film, Buffy the Vampire Slayer. So we're counting it.
4 of 10
In season 2, the Prison Break actor played Gage Petronzi, a member of the Sunnydale High swim team. To improve his performance, his coach gives him fish steroids and he ends up turning into a gill monster. Typical high school stuff.
5 of 10
Another high school swimmer with an unfortunate storyline! The actor played Sean Dwyer in the season 2 episode "Go Fish," and he was also transformed into a gill monster.
6 of 10
Fillion played Caleb, a super creepy and sadistic priest with a multi-episode character arc. (Fun fact: He auditioned for the role of Angel.)
7 of 10
The late actor plays Ted, Buffy's mom's creepy new boyfriend, in season 2 .
8 of 10
Another Buffy the Vampire Slayer (the movie!) performance we couldn't not include: Swank plays cool teen Kimberly Hannah.
9 of 10
In the season 7 episode "First Date," the R&B singer plays Lissa, a demon who tries to seduce Xander.
10 of 10
The actress plays Janice Penshaw, the best friend of Buffy’s sister, Dawn.
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