1- Dennis' cousin Marky drops by the Mitchell household for a destructive visit. This pint-sized terror pulls all kinds of pranks and Dennis gets blamed for them all. 2- Dennis is mistaken for PeeBee, and he's invited to a major University to work in their research lab. He accidentally creates a hologram that sets the entire institution on its collective ear. 3- Henry and Alice are going out for the evening and have a young man (a teenage version of Dennis) stay with Dennis. Dennis tries his best to out-fox his "sitter", but the sitter proves to be "one step ahead" of every prank Dennis can muster.