What if Minecraft Mobs suddenly achieved sentience? Well, that's what this mod is all about! This is an Origins addon that gives you all the abilities, good and bad, of every mob in the game (or as many as I've made). This mod is meant to work in conjunction with custom player models to not only give you the abilities, but the appearance of a mob as well, effectively turning you into the mob. The skins can be found on the Wiki, along with information on every mob currently in the mod.
Furthermore, with Custom Player Models, you can even customize how the skin looks in-game using that mod's skin editor! For example, I gave my Enderman a beanie!

How to make and edit skins is on the mod's wiki page, which can also be opened from the game.
You don't technically need that mod to use this one, it's not a dependency. But it will make it much more fun.
Here's some more images from the mod:

