This is a goofy detour where Beelzebub stops being a shounen action show and just lets Oga and Baby Beel solve mysteries like incompetent disaster twins. The comedy lands because it's grounded in how these two actually work together, not in random gags. You get three episodes of pure chaos investigation with zero stakes, and that's exactly what makes it work.

Beelzebub: Kaiketsu!! Beel-bo Meitantei Suiri is a set of three short specials from 2012 that shipped with volumes 14 through 16 of the Beelzebub DVD release. They are extras for the main series, and their genre labels point to a comedic take on mystery with supernatural elements. Viewers who already know Beelzebub are the natural audience for these bonus shorts.