totaly thought of the alien too, could it be some kind of cucumber ive seen some that have the feeding tenticles , granted not like that but could be.

Haha That's a perfect match.

Anywhere to keep it? Dont kill it if you dont need too! Its pretty cool looking hahaha

Looks to me like a goby of some sorts...

I agree with whomever said it was a spaghetti worm. I lot of sedentary annelids look pretty nasty when they come out of their burrows and tubes. Ever see a feather duster worm out of its tube?

Look up Terbellidae, the spaghetti worm family; a kind of polychaete worm (many-bristled worm). They look sort of like your blob in the pics of them out of their burrows. The rows of what look like bristles on either side indicate its some kind of segmented worm.

trust me i looked at pics.... it almost had a mouth of a puffer... super creepy!!! i have left it in the tank that I tore down. it didn't move so I'm pretty sure when it moved and it scared me.... and i threw it about 5 feet away it died then! lol!

worm
 

Medusa worm.i have a few in my aptasia tank-a type of cucumber that is a sand sifter-but mine are red about an inch to 1 1/2 inches long

doesn't look like any of those pics.... it literally looks like it was turning into something...not a worm though

looks exactly the same as the spaghetti worm I pulled out of my tank a few days ago. the tentacles are mostly retracted but it looks the same

like a goblin?? lol