SledgeHammer

Tried 21exp with no mods and 21 stable with mods and still same issue. Debug mode on, F6 to spawn entities and spawned "Zombie Guppy No Arms" It spawned that guy in the photo, and when you kill him, he starts to spin around and sometimes rises spinning in the sky.

These are awesome! One thing that I noticed, crawling armless guy is bugged. When you kill him, he starts to spin around and rises slowly up in the sky.