A "Bloop A Loop" is a person who acts in a retarded way. A "Bloop a Loop" is also something that one screams at someone else when angry to piss them off.
Joe : What ? Huh ? Durrrrr. * DROOLS *
Heather - Stop being such a bloop a loop !

Joe : Hey Heather.
Heather - YOUR SUCH A BLOOP A LOOP ! GOD.
Joe : WTF ?!?
Get the Bloop a Loop mug.