The Fairly OddParents (2001) : 5x27

Dad keeps trying to help Timmy with his homework. But he’s not the brightest dad, so any help he gives does more harm than good. How can Timmy get his dad to stop helping without hurting his feelings? He doesn’t. He completely avoids the subject by wishing that his dad was smart. Now that Dad has the brains of a genius, he home-school’s Timmy and pays a lot more attention to things like Timmy’s goldfish. In all the years that Timmy has had his pet fish, not once has he fed them. Dad concludes that they must be a new breed and sets out to dissect the fish in front of the entire scientific community.