Urusei Yatsura S01 E41 Duel! Ataru vs. Ataru

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

Ataru eats a lollipop Lum gave him and gets a mouth burn. Running off, he finds Cherry and a weird melon, which Ataru eats to cool his mouth. The melon causes Ataru to split into two Ataru's, one polite and the other casual. The two continue to fight all day.