Board Thread:Plants vs. Zombies 2/@comment-1764483-20150914192504/@comment-25154254-20150917230430

Thís is not a glitch. It is the system that is used to instantly kill all non-speed zombies when they are outside the lawn.

Only one non-speed zombie can be on one tile on the final column. But it is possible that they can be spawned on other tiles. There is no laziness from this, and Imp Cannon is a very different non-speed zombie. It still does move, so it can be stacked. But for Zombie King and Fisherman, they do not move at all and they are like "plants", they take whole tile. There can't be more than 5 zombies on one column, but there can be if these spawn in various columns. Spore-shroom is also a great example, as he can't spawn new clones on the tile that is being taken.