Urusei Yatsura S01 E109 Outraged! Piteous Kid Shutaro!!

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

Ataru, Lum, Shinobu, Mendo, and Ryunosuke go back in time to when Mendou was an obnoxious, violent kid to cure him of both his nyctophobia and claustrophobia.