Urusei Yatsura Movie 3: Remember My Love
Japanese title: うる星やつら リメンバー・マイ・ラヴ
Type: Movie
Source: Manga
Episodes: 1
Status: Finished Airing
Aired: Jan 26, 1985
Duration: 1 hr 35 min
Rating: PG-13 - Teens 13 or older
Studios: Studio Deen
Producers: Kitty Films
Licensors: AnimEigo, Discotek Media
Genres: Action, Adventure, Comedy, Drama, Romance, Sci-Fi
Demographics: Shounen

It seems that when Lum was born, a postal screwup resulted in a witchy friend of the family not getting an invitation to the celebration. The witch put a curse on Lum, that she would never be happy with her True Love. 

In the present, a new Amusement Park has been built in Tomobiki, and opening day finds the whole gang sampling its pleasures. At a magic show, however, Ataru gets turned into a large pink hippo-potamus, FOR REAL! 

When Lum attempts to track down the magician that transformed her Darling, things start to get very weird, very fast! 

(Source: AniDB)