It is about a blond kid who basically sucks at everything. He helps a witch who rewards him by granting him one "wish" for one day. He then found a bit of a cheat and said he wanted to be the best at everything. She said that it would only last one day, but made a mistake and made it permanent. Then, the next day, he was able to read at a college level and spit so hard he broke a street light. Also, whenever he flexed his muscles, it would comically go up like five feet.
I watched it around the 2000s, so it was probably made around then. It is driving me crazy that I know this much, but I don't remember what it was called.