While riding in the passenger seat of a boat, the model of some mobs do not properly fit within the boat. This causes them to appear with their legs hanging out the back of the boat, which looks extremely awkward. This does not seem to be intended behavior, as the player always fits within the boat properly, and mobs do as well when they are by themselves.

A solution to this bug would be to follow the example of the Pocket Edition, which rotates mobs in the passenger seat sideways, to allow them to fit into the boat properly.