Bat
From SuperTux
Behaviour: zigzag flight, eats Ants - Can zero in on Tux
Look: A Bat
Hurt Tux: like Snowball
Hurt it: jump or spit
[edit] Alternative
Flutters up and down, upon seeing Tux dives and tries to catch him (much like Zeekling).
Perhaps in Ghost Forest, a Spooky Mr Tree could, when jumped on, release bats instead of Poison Ivies. They could fly straight up into the air, then zoom in on Tux. If Tux dodges the could hurt they ground and get stunned, ay which point Tux could jump on them.
[edit] Alternative
This would work if Ghostly Tree was to release two bats. They could fly up to the top of the screen and then fly straight down at Tux, who would have to dodge at the last moment. If he succeeds, the bats would be 'stunned,' at which point they could be squished.
Diagram:
