5. The Water Slide On The Stairs
Peter is standing at the top of the staircase in his house in the episode "Fast Times at Buddy Cianci Jr. High". He's wearing swimming shorts and holding a hosepipe which is running water all the way down the stairs and proudly tells Brian that he's made a waterslide in the house. He proceeds to use this "waterslide" and, as you would expect, badly injures himself. Whilst he is crying out in agony, Brian calmly continues reading his newspaper and tells Peter that he isn't going to call for medical help because Peter won't learn anything if he does. Rightly so Brian! What a complete idiot.