In World of Warcraft: Cataclysm, Blizzard has added a mini-game version of "Plants vs Zombies" by Popcap as a series of 5 quests. To reach the quest vendor, go to Brazie Farmstead in Hillsbrad Foothills (northwest of the ruined town of Southshore).

The first quest is called "Basic Botany" and is basically a tutorial level.



In the second quest, you get introduced to the Sunflower which is used to generate additional solar energy. You will always want a minimum of 5 sunflowers, with 8-10 being preferable in the later levels. That's really the key to the later levels because without solar power, you can't plant or replace plants fast enough to keep up.



The third quest introduces you to the Rocknut and Freezya plants.



This is a tough level that introduces the Pumpkin bomb plant. Personally, I found that the tentacles backed up by a Freezya and Spitter worked almost as well.



In the final level, you go up against a boss mob and lots and lots of zombies. Once the quest chain is complete, you cannot do it again on that character. The reward is a few low level items and the "Singing Sunflower" pet. You will need to replace plants that get killed by the orange gas and keep at least 7 sunflowers alive at all times in order to keep up with plants that are killed by gas or zombies.