Unless you played like agents like Kerrigan was. Then again. *shrugs*
I'd have Zerg in World of Starcraft be able to evolve their shape as they gain levels. More appendages, teeth, tails and such.
They'd also be able to have a 'human disguise' form where those stuff would be hidden.
There'd be four 'classes' available for the Zerg:
Slayer - large, brutish, combat oriented
Hunter - most human looking, stealthy, deadly assassin
Defiler - spellcaster class, uses viral clouds and ugly stuff like that
Harbringer - 'pet' class, being able to spawn smaller zergs to assist it