Fusion is a technique performed by several of the Z Fighters in DBZ. The Fusion Dance was used by Goten and Trunks to form Gotenks and also by Goku and Vegeta to form Gogeta. The Fusion Dance only lasts 1/2 an hour. Another type is to use the Special Fusion Earings called Potura (I think that's how it's spelled) whiched form Veggetto (Goku+Vegeta) in the Buu Saga. This type of Fusion is permanent, but when Veggetto was absorbed by Buu, they seperated back to normal. The last type of fusion was used by Piccolo, Nail and Kame-Sama which is Namek Fusion.