The show follows the lives of the Mitchell family – Henry, Alice, and their only child, Dennis, an energetic, trouble-prone, mischievous, but well-meaning boy, who often tangles first with his peace-and-quiet-loving neighbor, George Wilson, a retired salesman, and later with George's brother John, a writer.
While the series was based on theDennis the Menacecomic strip, there are differences between the two. On the sitcom and in the comics, Dennis is basically a good, well-intentioned boy who always tries to help people, but winds up making situations worse – often at Mr. Wilson's expense. In early episodes of the first season, more outlandish disasters occurred as a result of his actions. The character of Dennis was toned down by the sixth or seventh episode. Instead of Dennis's dog Ruff, a smallerCairn Terrier(per the episode "Miss Cathcart's Friend") named Fremont belonged to George and Martha Wilson. He did not appear during the fourth season, when John and Eloise Wilson moved into 625 Elm Street.