Dragon Ball Z: Fusion Reborn

The trouble starts when a careless teenage...heaven dweller, neglects to change the tanks of the "soul laundry machine", which cleans souls that are going to hell. When the tanks explode, the heaven dwelling kid becomes possessed and turns into Janenba, a huge blob-like creature. Janemba changes the laws of the afterworld and creates much havoc, including bringing such characters back to life as Furiza and his minions and all of the other dead. Pikehan and Goku try to free the Demon lord and distract Janemba, it becomes evident that this tubby bastard's magic is almost invincible. While Pikehan shouts insults at the Demon lord's prison, Goku strikes back against the Jell-o menace. It looks as though Goku has won, when Janenba transforms into a smaller, deadlier fighter, whom Goku cannot defeat. When Vegita shows up, he too realizes that he cannot beat Janenba, so Goku convinces Vegita to fuse with him. Unfortunately, Vegita screws up the fusion dance, which is amusing in and of itself, and they turn into fat Gogita for 30 minutes. During this moment of weakness, Gogita gets the living snot beaten out of him. Meanwhile, Gohan, Videl, Goten, and Trunks are taking care of the masses of undead that now walk the Earth. They prove to be no match for our seasoned warriors. When the Fat Gogita transformation wears off, Pikehan buys Goku and Vegita the time to fuse correctly. In this new form of Gogita, Janemba is easily defeated and the rules of the afterworld return to normal and the generic happy ending ensues.