You can't help but laugh when...

...you walk in your son's room with every intention of disciplining him for not being in bed during nap time, only to discover that he has decided that he didn't like the Pull-Ups he was wearing and has taken them off and changed into the Elmo underwear he found in one of his drawers.  This situation becomes even funnier when you realize that he put them on backwards and yet is still quite pleased with himself.