Just wanted yall to know that hostile spawn eggs aren't working in superflat worlds. I have tried them in the last 3 snapshots and cant get them to actually spawn. Passive mobs will spawn, but hostile and neutral (except the polar bear) do not seem to want to finish the spawn process. Pigmen, Endermen, Skeletons, silverfish you name it will spawn for about 1/2 a sec and then despawn.

When subtitles are enabled it will show, "enderman/(mob) hurts" but not that it dies. The spawn eggs seem to be working fine in a regular world, but I just thought I would bring it to your attention about the superflat issue. I would add a pic of it happening but I cant catch it quick enough for a screenshot.