Can someone ID this?

[theracenut]

It appeared in my tank. I assume it hitchhiked on a piece of live rock. We call it the blob it has been in the tank for 8 months or so. It does not move it swells at times. It has two holes that open and close I assume it is either breathing or eating. Nothing bothers it and it bothers nothing. It looks like a butt for lack of a better description. What the heck is it?

 

[skinz78]

First thought, it's Jabba the Hut LOL!

It looks like some type of a sea squirt to me.