Basically, the name means what the name suggests, a dance in which two fighters perform a dance to fuse into one whole being. Most of you probably remember the Fusion Dance from the Buu Saga, when Goten and Trunks used the Fusion Dance to make everyones favorite cocky bitch, Gotenks. But, actually, they were not the first people to use it. The first person was Goku. He learned this style of fusion during the five years of inactivity between the end of the Cell Game and before Gohan's start at Orange Star High School. The fusers must be similar in size, build, and powerlevel (The stronger fighter can simply just lower his powerlevel to match the fighter with the lower powerlevel to meet this requirement). Any mistakes in performing the dance can cause defective fusions. This form of fusion only lasts for exactly 30 minutes, so after this time period the two fighters de-fuse into their own two beings. It hasn't been successful to break the fusion before or after the 30 minute time period.
The fusion technique of choice for Kaioushins, this technique is allegedly hundreds of times better than that of the "Fusion Dance". The two fighters that wish to fuse had to wear an earing, each having one in the opposite ear of the other fighter. After this is done, they can fuse into one being (Which in prospective causes the final being to have 2 earings on). This fusion was meant to be permanent, but unexpected conditions caused the break-up of the two fusers. One examlple of this is in the Buu Saga, when Vegeta and Goku put on the earings to make the Super Strong warrior, Vegetto. This fusion was supposed to be permanent, but when they were spit out of Buu's stomach (after they had been absorbed), the fusion wore off some how.
The way of fusing by the Namekians. This is a way for 2 Namekians to fuse into one being. No special objects or performances are needed for this type of fusion. The fuser just has to place his hand on the person that he wishes to fuse with (being that the person being fused allows the act), and they just merge into one. There are no set time periods for this type of fusion, and the two fighers can de-fuse at any point of time. The only two times I have ever seen this done is in the Freeza Saga (when Nail and Piccolo fuse to fight Freeza) and in the beginning of the Cell Saga (when Piccolo and Kami Fuse to battle Cell) When you think about it, Piccolo's body is kinda full!
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