Sylvester and Junior start work as mouse catchers at the Museum of Natural History, where Sylvester has taken his son to work for the first time. Junior has never seen a mouse, and when his dad’s unable to catch the first one of the night, Junior grabs it and asks what all the fuss is about. Sylvester has always lied about the size of mice, and now he must try to impress his son. “You see, son, mice come in assorted sizes. Little runties, like the ones around here, and king-size mice like I used to hunt,” Sylvester brags. What he doesn’t know is that a baby kangaroo has broken into the museum. His boast is tested when the pair encounter the kangaroo. When both father and son mistake the kangaroo for a mouse, Sylvester is going to be hurtin’ for certain.