Put the summary of the bug you're having here
I was playing 1.3.2 on a server and 1.4.2 in single player when I saw zombies, skeletons, spiders and endermen with slimes on thei heads from big to small, at first I thought it was a client side visual bug but then my friend saw it(1.3.2 server) and I was able to kill it and it gave me a slime ball so it wasn't a visual or client side bug the same thing happened in a survival 1.4.2 world(And the biomes were both extreme hills).
What I expected to happen was...:
Describe what you thought should happen here
I expected it to be a visual client side bug but it was neither.
What actually happened was...:
Describe what happened here
(same as summary above) I was playing 1.3.2 on a server and 1.4.2 in single player when I saw zombies, skeletons, spiders and endermen with slimes on thei heads from big to small, at first I thought it was a client side visual bug but then my friend saw it(1.3.2 server) and I was able to kill it and it gave me a slime ball so it wasn't a visual or client side bug the same thing happened in a survival 1.4.2 world(And the biomes were both extreme hills above ground ).
Steps to Reproduce: This doesn't always work when you try to reproduce.

1. Go to an extreme hills biome and spawn a bunch of skeletons, zombies, endermen or spiders with a bunch of slimes (all in a close space). (when I first found the bug they spawned by themselves)
2. Log out and close Minecraft then come back in
3. There is about a 5 percent chance you will get a aggressive mob with a slime on its head.