shrimp brain

Simply some one who is rather dimwitted and stupid or does something, says something idiotic or stupid.

Bob - Where did I put those keys?

Andy - In yer pocket, shrimp brain.

Shrimp brain

Shrimps shit with their asshole, which lies on their forehead. So basically an alternative to "shit head".

-Dude, where's your apartment?
-You asked me for the 6th time this week you shrimp brain.