User blog comment:Willbachbakal/Classes & Subclasses My Way/@comment-22636720-20160427042313/@comment-1330314-20160427050357

Lesdin has it right, a champion can have different builds, but that doesn't really change the core class/subclass(es) they belong to. I personally think Fizz has some Strider elements to him (he deals a lot of autoattack-based damage and has some form of innate protection with his passive and E), which is what his AD and tanky builds capitalize on, though ultimately his core intended function is to jump into combat, kill people quickly and retreat, which makes him an assassin first and foremost (as for what subclasses he'd fit in, he's probably closest to Hunter, though he's got a bit of Rogue going on too).