Zombie like thing opening my doors

Twice now I've been in my home and heard the door open and shut and look at it to see a creature walk in. It looks almost like another player but I'm in single player mode and it attacks me. They both had names over their heads and one of them dropped two rotten flesh when I killed it.

What are they and how do I stop them from getting in?

Solution 1:

This is a mod called HeadCrumbs.

So Infinity 1.0.2 added the HeadCrumbs mod, which adds a bunch of humanoid mobs with skins of minecraft "celebrities".

I'm afraid there's not a lot of documentation to be found about them, but assuming they are supposed to act somewhat like a player, using an iron door or easy difficulty are reasonable guesses for how to keep them out.