Pop a germ of size 25x or greater

Playing from stage 1, fall through the deck after Smithers.

Collect all the bonus flowers in the game

Finish the Unfinished Empire chapter.

Win a Two-Headed Giant game.

Defeat the Dreadnaught - successfully complete Act 2

Defeat Pyro without any player using mutant powers.

Grow all the flowers on every level

Win a Multiplayer game.

Increase your life total to 30 or more in single player, or 60 or more in Two-Headed Giant

You've put down a power holder.

Survive for 5 minutes or more in Arcade Mode