Venustoise

Venustoise is an infamous Pokémon that debuted on episode 20 of the Pokémon anime, it was components of a Blastoise and Venusaur, when a Gastly was confronted by Ash's Squirtle and Bulbasaur, he fused Blastoise and Venusaur together, thus making this Pokémon Fusion, making an interest of people making their own Pokémon Fusions, it has become really popular since it's appearance.

Trivia

 * It's similar to Dragon Ball Z, where two people can fuse together and make a single body.