Tanoshii Moomin Ikka: Moomindani no Suisei

Unusual things have been happening in Moominvalley. Moomin, Sniff and Mee leave for the Observatory on the Lonely Mountains to confirm the Muskrat's words: a comet is about to hit Moominvalley and destroy everything. On the way they meet Snufkin, the Hemulen and the Snorks and experience many adventures.

(Source: Anime News Network)