Plants vs. Zombies Garden Warfare

When playing Gardens and Graveyards as a zombie, you will see piles of bones laying around the map. Run up to one and activate it and spawn any zombie from the list to get the achievement. These work the same as the potted plants.

In order to unlock this achievement, you will need to join a game of Gardens and Graveyards as a Zombie (classic or normal, both are fine, but I recommend classic so it's harder for the players to vanquish you) and find a pile of dirt and bones on the ground. Simply go near it, press to open the selection menu, select which zombie you want to summon, and boom, achievement.