Co-op Mode

Co-op mode is a feature added in the XBLA version and PSN version, but not in the DS version (Although Vs. Mode is present in the DS version).

Co-op Modes
The Co-op mode has Co-Op Day, Night, Pool, Roof, Bowling, Zomboss, Day: Hard, Night Hard, Pool Hard, Roof Hard and Endless.

Co-op is pretty much like Survival Mode but the normal Co-op levels have 2 flags (and three) instead of a full Survival level while Co-op hard levels are exactly the same as Survival Hard levels.

You can also Butter any zombie in any co-op mode by holding down the "x" button for a second. It will paralyze the Zombie that is highlighted, but the butter won't damage the zombie.

Trivia

 * For some reason, Co-op Mode does not have Co-op Fog and Fog Hard.
 * This is probably because it would be hard to deal with the Zombies in Fog.
 * No matter how many seed slots you have, you and your partner will always have eight slots total.
 * Perhaps this is because it would be unfair to you or your partner to have less seeds than the other, when the player has an odd amount of seeds (7 or 9).
 * This mode is different from Versus Mode, because both of the players control plants.
 * It is unknown why Dancing Zombie and Digger Zombie appears on the Co-op Roof & Co-op Roof (Hard).