a retarted
A person who has the brainpower of a pop-tart. Like, it's so weak it can't even hold up a basic math problem.
My cousin has the brain of a pop-tart. He thinks 2+2 is 5.
My teacher called me a pop-tart for not knowing what 2+2 is.
My dog has the brain of a pop-tart. He thinks I'm a retarted.