Parrot

The hostile bird and the pet bird look almost identical, so if your pet is out when an invasion lands you will spend the fight swinging at the wrong one. The enemy version is slightly larger, and on a crowded screen that is the only difference you get to work with. Put the pet away before the wave arrives.

It flies straight at you for contact damage and has nothing else in its kit. With no target in reach it perches on whatever block is handy, the way vultures do, so one can sit quietly on a roof and drop on you as you pass underneath. It also only arrives with the invasion on foot: the flying ship later in the event cannot produce them, so every parrot you meet walked in with a ground wave.