Brain Damage (1988)

Wow, this is one odd little movie.  Brian isn't feeling well.  So he cancels a date with his girlfriend and goes to bed early.  When he wakes up, he finds a pool of blood on his bed and a wound in the back of his neck.  He also feels like someone is watching him and soon discovers it's Elmer the Aylmer, a little alien monster who is phallic in appearance and speaks with the voice of horror host Zacherle.

Turns out Elmer has been living with the people in the upstairs apartment who have been feeding him cow brains so they can control him.

When Elmer injects Brian's brain with a blue liquid via the hole in his neck, Brian starts hallucinating, sees colors, and has a euphoric high.  This also anesthetizes him so that he doesn't remember what Elmer has done while they're out.

With Brian as a source of transportation, Elmer starts searching for human brains to eat so he can restore his power.  Brian's fine with that as long as Elmer gives him a blast of brain juice.  Brian is addicted after one hit and enjoys the high. Plus he doesn't want any rememberance of Elmer attaching himself to some poor girls forehead and consuming her brain while she screams and flails in vain.

There is one scene in which Brian's pulling bloody gunk out of his ear, and his ear falls off. This starts a deluge of blood that is impressive.

This is a pretty cool movie overall.  Watch for The Swimming Pool Q's performing in the club scene.