Hexafusion / Triple Fusion - a format that also has character

Thanks I hate it.

The Shrek-Leela combo is a reference to Leela's parents, one of which (her mother, Turanga Munda) is an Octopus mutant. Leela herself is so normal for a mutant she is often mistaken for a Cyclops, since her mutation is the eye (shared by her parents) as well as a singing butt boil, though that's less a ground-in-basis mutation and more a one-time dramedy gag for how often it appears.