Tottoko Hamtarou OVA 3: Hamuchanzu to Niji no Kuni no Oujisama - Sekai de Ichiban no Takaramono
Japanese title: ハムちゃんずと虹の国の王子さま 〜せかいでいちばんのたからもの〜
Type: OVA
Episodes: 1
Source: Unknown
Genres: Adventure, Comedy
Studios: TMS Entertainment
Duration: 45 min
Rating: G - All Ages

Based on the third Hamtaro game (fourth in Japan), Prince Bo falls from the sky when the rainbow disappears. Now Hamtaro and the Ham-Hams must help him bring back the rainbow.

(Source: Wikipedia)