The idea is to get a token creature out - flayer husk, wind zendikon, lab rats. Cast either polymorph or proteus staff on it.  The only real creatures in the deck are fatties, so you replace the token with a fattie. 

Obviously emrakul or progenitus or something would be better than whatever budget fattie I've got in there, but that's more value than I want to put in this deck.