Kaettekita Dr. Slump: Arale-chan Special
Japanese title: 帰って来たDr.スランプ アラレちゃんスペシャル
Type: Special
Episodes: 1
Source: Manga
Genres: Comedy, Sci-Fi
Studios: Toei Animation
Duration: 1 hr 12 min
Rating: PG-13 - Teens 13 or older

This is the last episode (243), and the 4th movie, “The Treasure of Nanaba Castle” with a wraparound plot of new material, including an older Turbo and the wedding of Tsukutsun and Akane.

(Source: AniDB)