Marge is briefly seen in her regular clothes as Homer is racing home to her show. Before Homer leaves, and after he crashes into her sculptures, she's in her Sunday dress.
When Homer is getting dressed as an ice cream man, we see he needs two belts to get around his waist. Therefore, he has a buckle on his back waist as well as his front. In a couple of brief shots, the buckle on his back waist is gone. This happens BEFORE Homer rips his pants and is replaced with a belt that goes around all the way.
Before Homer comes across the Divorced Dads' Visitation Jamboree, the wheels on his ice cream truck do not turn.