No good deed goes un-punished.

Let's say you land on a planet and open the door to an alien with three tits and she seems nice.    You say to the crew she looks okay to let aboard.      Hell she needs a bed and some food.    Why not let her join the crew?     All seems good and you let her come in.     Hell you convince her to allow you to screw her five holes.     It's all good.   She is eating and sleeping, enjoying the time with you.     Till you wake up the third night with the bitch sucking your brains out from your ears.    Most of your crew has been eaten too.     No good deed goes un-punished, it's a universal thing in the universe.    

                                           Old Vampire movie form the 60s brings the whole thing

To Life!