Episode 34 of "Sabrina, the teenage witch"
s02e10 To Tell A Mortal
Title: To Tell A Mortal
Original Air Date: 11/21/1997 on ABC
Plot Outline:
It's Friday the 13th, which Sabrina learns is the day witches can tell mortals the truth about themselves because everyone's memories will be wiped clean once the day ends. Despite warnings from her aunts about bad consequences, Sabrina decides she can trust Valerie and Harvey to take the news in stride, and grants them each a wish: Valerie gets to dance with Drew Carey, and Harvey gets to meet baseball giant Mark Langston. But there's inevitably trouble: Libby overhears the news and alerts both the PTA and the media. Happily, Valerie and Harvey save Sabrina's bacon, proving that they are true friends even though they will now forget her secret again.