It's a Birthday Party, Dajo / Iyami's Great Discovery

Osomatsu-san Movie: Gekijou Koukai Kinen - Original Tanpen Gekijou · Episode 6 · “It's a Birthday Party, Dajo / Iyami's Great Discovery”

A short series depicting side stories about the brothers' daily life, released on dTV streaming service. It received an advance screening together with the movie on March 7 in Tokyo. (Source: AniDB)