Several races can perform a fusion between two (and in one case, three) player characters to become a more powerful race.
Note that in each instance, only the Dominant partner in a fusion will receive the upgrade and remain playable. While each case varies slightly, for any fusion you will need to: remove any equipment you wish to keep from the secondary character; release any racial ranks held by either character; have both characters power down completely; have any characters involved in the fusion in the same room.
You will need A Potara Earring (left) on the dominant character and A Potara Earring (right) on the secondary character. Both characters require a base powerlevel of at least 1,000,000,000. An Immortal is required to perform this type of fusion.
This type of fusion is performed by players without the need of an Immortal. The two characters must first Partner each other before performing the fusion. The character that uses the racial Fusion skill will become the dominant.
Super Namek requires a base powerlevel of 400,000,000,000.
Terran-Golem requires a base powerlevel of 4,000,000,000.
Hellfighter requires a base powerlevel of 4,000,000,000,000.
This fusion requires one of each -H, -E, and -FM type Android each with a powerlevel of at least 300,000,000,000. An Immortal is required to perform this type of fusion.