Urusei Yatsura S00 E09 I Howl at the Moon

"Grab her horns and she might just become your darling!"

Lum makes some sakuramochi for Ataru to enjoy flower-viewing together. However, she mistakenly made something that is not suitable for human consumption and turns Ataru as well as Onsen-Mark into wolfmen, thus she must quickly prepare an antidote and force an elusive Ataru to take it or he’ll remain a wolf forever.