fusion

A combination of two or more characters leading to a new character.

crossover_cosplay / cosplay - The character is merely wearing the clothes and/or hairstyle of another character.
hybrid - The species equivalent.
merging or conjoined - While either of these tags can overlap with "fusion", if multiple characters are literally being physically merged or conjoined together, "merging" or "conjoined" should also be used.

The following tags are aliased to this tag: character_fusion (learn more).