Easter Eggs and Hidden Details in Plants vs. Zombies.

Sunglasses and Mustache

While playing the game, type Future to give zombies Sunglasses and type Mustache to give them mustaches.

Lex the Bookworm

Go to Achievements and scroll down to see a worm with glasses. He is Lex the Bookworm from Bookworm Adventures game.

Chinese Zombies

Go to Achievements and scroll down to bottom of the page to see Chinese Zombies.