Lederhosen of Doom is the first half of the 14th episode of Dave the Barbarian.
Fang gets some pants sent by her parents and doesn't bother to read the note that came with them. This is problematic, because the note explains that the pants are the evil trouser beast and will take control of anyone who wears them. Fang loves the pants at first because they give her fantastic strength — at last she's as strong as Dave! But soon the pants take her over, using her as a tool to get revenge on their hated foe... Oswidge.