One of the main concepts of many shōnen manga from the beginning is the idea of several different characters, each of different backgrounds and ideals, coming together to fight against a common foe. However, there are times when two or more characters must literally "come together", uniting in order to become stronger and stop something more powerful than the individual parts. This is the concept known as fusion and is a staple in certain shōnen series. Most famously, the shōnen series Dragon Ball Z utilized the fusion concept, with characters such as Vegetto and Gotenks being the final result of various fusion methods such as Potara Earrings or the Fusion Dance. Although the characters are united as one, the composite keeps many of the attributes, both in power and personality, of the two or more components.

Because of its nature of being a shōnen manga/anime series, Bobobo-bo Bo-bobo incorporates fusion as one of the many power-ups the main characters can utilize in battle. However, due to the satirical and parodying nature of this shōnen series, the fusions are slightly different than a typical series. Bo-bobo, the main human character, is the main receiver of all fusions, with the component parts coming from various non-humanoid characters, including the orange, star-shaped being Don Patch, the blue jelly being Tokoro Tennosuke and the small white mascot Dengaku Man. When Bo-bobo fuses with one of them (or more than one on occasion), they usually enter his body through an opening—usually through his mouth, but occasionally through his openable golden afro or (on one occasion) through his pants. When the fusion occurs, the final result is usually nothing like either Bo-bobo or whomever he has fused with. The new being may have a different personality from the two components (e.g., being serious instead of being crazy), have a different appearance unlike either of them (which is usually human, but bears no resemblance to either character), or may even be of the opposite sex. Furthermore, there can be occasions where one component may change the direction of the possible fusion, making Bo-bobo transform into something completely different from what was expected. It is this unpredictability regarding the fusion concept that makes these combined forms as memorable as the characters they originally come from.

Incomplete FusionEdit

This means is usually a result of when a fist master's fist skill is incapacitated. A few examples of this would be Incomplete BoboPatch, as a result of Bo-bobo and Don Patch being turned into little kids and Poorly Drawn Shinsetsu Tenbobo, when the Neo Maruhage Academy Four Heavenly Kings seal away the fist skills of Bo-bobo and Tokoro Tennosuke.