'Eggo Brained' is a term used for people who intellectually are intelligent, but lack street smarts. Effectively making them a complete utter dumbass even when faced with the most easy problems. Like using a microwave, doorknob, or fixing the oven door.
The phrase was coined after Frank Dorsa somehow fucked up waffling a waffle and created Eggos.
You eggo brained retard, how do you have straight A's yet you don't know how to use a dishwasher?