I think there are loads of easter eggs in this game. In the acheivements I found a green worm (lex), 5 gems from bejeweled, a chuzzle from chuzzle, some dead unicorn from peggled, a pipe from rocket mania, a weird idol thing from zumas revenge and zombie china (a reference to "you could dig ur way to china from the us") i know all this coz i look at every page in this wiki and i played a free trial of all the games from popcap and bought plants vs zombies.