Dragon Ball's Fusion is the fusions used by characters in the manga and anime Dragon Ball. It is used as a meme by choosing characters from a different franchise and fusing them.

About

The fusion is done by two ways, by doing the Metamoran dance, where a two characters have equal Power Levels, then in a synchronized pattern, both arms swinging up pointing to another direction while pacing towards each other, then swinging them back to the first position but holding one leg up (depending on the side you are on), then while in the middle of swinging to the second position, point your index fingers at the other's, completely mirroring each other, while saying "FUUU, SION, HAAA!". The characters will be fused for thirty minutes. The other is the Potara earrings, where you put one earring on one while the other character will put the other on his opposite ear to the one you put it on. No equal power levels are necessary. If you are a divine being like a Supreme Kai, you will stay fused forever unless you are a mortal in this case you would be fused for an hour.

Origin

Both fusions originate from the Majin Buu Saga of Dragon Ball Z. Goku has learned the Metamoran fusion in the Other World, and teaches the technique to Piccolo so that he can properly teach his son Goten and his friend Trunks to master it in order to defeat Majin Buu.

The Potara originates later into the arc when the Old Kai teaches Goku and Gohan that the Supreme Kai's Potara earrings can fuse people forever. Goku and Vegeta use them to become Vegito while fighting the new Super Buu that absorbed Gohan.

https://www.youtube.com/watch?v=z5yIapnxHr8

Spread

The earliest known memes about the fusions was back in 2002 where many anime fans on sites posted pictures of characters such as Sonic The Hedgehog and Super Mario doing the fusion dance.

There was a parody made by the Pokémon anime where Venusaur and Blastoise do something similar to that of the fusion dance making the "Venustoise". These are now under the name Pokéfusion.