Willie makes his major appearance in three episodes:
In the episode "Heat", while the children tries to get some ice cream due to the heat. Willie charges them 20 dollars (which the children don't have enough money for ice cream). Eugene wanted to take a snow cone, and Willie charges 18 dollars for that. But Eugene had 70 cents and askes what he will get for 70 cents, then Willie laughes evilly and yelled out "nothing". Later Arnold started a riot against Willie and chanted "No ice cream no peace". Arnold had tries to stop the riot and stand up for Willie, but the children tried to flip Willie's ice cream truck. Then the rain comes, and Willie drives away from the children.
In the episode "Career Day", Willie has become a terrible mentor to Arnold, having him sit in the freezer, can't talk to customers and can't handle money. Then Willie evilly threatens to give Arnold an "F" and soon after Willie's boss/dad comes amd say that if he doesn't sell his whole stock by 6:00 that he will be fired. Then Arnold learn about Willie's perspective. Arnold agrees to help him sell his whole stock. Arnold teaches Wille to be more friendly to his customers and earned the respect of the neighorhood children. While a half of freezer full, Willie sells out his whole stock to the other kids and thier mentors for Career Day. Willie keeps his job and give Arnold an F (for Friendly), but Arnold actually gets an "A". Then Willie tells his boss/dad that he win this time.
He is the main antagonist of the episode "Grandpa's Packard", Wille gets into an accident by Phil, and Willie decided to started get revenge on Phil. Willie followed Phil to the Car Show and disguised himself as Ivana Divancevic and has steal Phil's packard and painted it red. Later Arnold and his grandparents caught Willie and he admits it to get even with Phil. After the police arrives, Willie apologizes and Phil forgives him and won't press charges if he paints the packard green again.