User blog comment:Uselessguy/Guess Plants or Zombies in the whole series/@comment-25154254-20141024025613/@comment-24828059-20141024151313

Dr. Zomboss. After you defeat him in Adventure Mode, you'll fight him again in Dr. Zomboss' revenge.

Iceberg Lettuce. If you plant one after Zombot Sphinx-inator is defeated, it will freeze him when Zomboss attemps to teleport.

Cob Cannon, Chomper and Spring Bean (PS) are reusable instant-kills.

Gas Can Zombie added "un" before "dead end" in the PvZA trailer. (Mean that's not the end).

Dancing Zombie. After the back-up dancers are killed, he will summon more.