Dennis Mitchell
This superactive young upstart has been "5 an' a half" since he was first created in 1950. He's too young for kindergarten and too old for the playpen. He's active, agile, tireless and hard to catch. He's also inquisitive, imaginative and of an experimental turn of mind, which frequently lands him in situations he can't always control. With his impish grin, he delivers sometimes blunt observations of the truth. While never malicious or mean, the irrepressible Dennis remains a threat to property, the pomposity of adults and quiet afternoons. He's an All-American handful and every day is "trick or treat" for almost anyone in sight.

Alice Mitchell
She brooks no nonsense, orders Dennis into his corner chair when necessary, and spends considerable time on her knees at the bathtub cleaning the grime from her adventurous offspring. Although often harried, flustered and provoked to tears, this trim and attractive mother of our short hero is loaded with patience, energy, logic and love to spare. She keeps her small house clean and tidy, always fresh-smelling, the perfect oasis of comfort and joy when her husband arrives from the office to spend quality time with his son and take her off the hook. She is forever grateful for having neighbors like the Wilsons, but she can hardly wait until Dennis finally enters the first grade.

Henry Mitchell
With a kiss and a wave, this gangly 32-year-old aeronautical engineer leaves home promptly each morning and avoids the many misadventures that occur in his neighborhood during his absence. He will receive an occasional "Mayday!" call from his wife and, to the apprehension of the staff, Dennis and his mom will sometimes drop by the office for a brief visit. Henry plays his most important role when he arrives home each evening. He listens to his son's escapades while trying to read the newspaper; he indulges in a little horseplay; and after dinner, he'll end the day with a good-night story for his son. Then, of course, there's always the delayed call for "a drink of water."

Ruff
Ruff is Dennis's ungainly but amiable canine of uncertain ancestry whose characteristics include large paws, stringy ears and lots of long hair. Dennis gives him the affection and companionship that might otherwise go to a brother.

Hot Dog
After his new cat devoured an entire package of wieners, Dennis exclaimed, "I'm gonna call you HOT DOG!"

George Wilson
The portly George Wilson retired from the Postal Service hoping to enjoy his Golden Years far from noisy children and yapping dogs. He's often found puttering in his rose garden, fussing over his stamp collection, or lounging in an attic full of boxes of photo albums, an old hunting canoe, ancient golf clubs, stacks of National Geographic and Life magazines, a Victrola, and his prized accumulation of classic jazz records. George and his wife Martha are childless, but a short, tow-headed boy next door has filled the vacuum, driving poor George almost to distraction but bringing much-needed love into the otherwise quiet life of the Wilsons. Dennis has a jillion questions and lots of time while George has all of the answers but little patience.

Martha Wilson
A plump, good-natured and understanding lady, Martha has been married to her well-meaning fusspot husband George for nearly 50 years. She loves Dennis as though he was her own grandchild. Her home is spotless and her kitchen smells like heaven, especially to Dennis. After a welcome cry through the window, he usually quietly enters through the back door to enjoy a sample of whatever has just emerged from Martha's oven and chats with the gracious hostess until the retired grump brusquely ushers him out the front door. Martha's biggest regret is having no children of her own, but she more than makes up for it by spreading her motherly warmth and charm to all of the neighborhood children. Every neighborhood should have a Martha Wilson.

Grandpa Johnson
Alice's father is a short, debonair widower, with a bounce in his step, a twinkle in his eye, and an enthusiastic attitude. He visits twice a year but seldom stays long, more than likely because he must share the bedroom with Dennis. But he plays the grandpa game to the limit, spoiling the young lad in every way, much to the disdain of next-door neighbor George Wilson, who pouts and growls that Dennis is really HIS grandson. George has often lamented that "Swede" Johnson comes around just to "grab all the glory, then disappear into the sunset," leaving poor George to cope for the rest of the year as the suffering, surrogate grandfather.

Joey McDonald
Younger and shorter, he's Dennis's shadow. Joey eagerly learns various facts of life from his neighborhood hero. Shy and a bit nervous, he is afraid of ghosts, goblins and anything else he can't see. Still, he and Dennis are the very best of friends.

Margaret Wade
This bespeckled redhead is a bit taller, two years older and, she thinks, MUCH wiser than her heartthrob, Dennis Mitchell. Margaret knows Dennis has great potential, but badly needs shaping up under her guidance — she has grandiose dreams of a romantic future and lots of children. Dennis tolerates her piano playing as long as the cookies hold out. In fact, Margaret's cookies and fudge are the cement that binds their relationship together, however shaky it might become. She keeps coming back in spite of rebuffs, insults, put-downs and outright total rejection. All of this fazes her only momentarily, for her mind is made up.

Gina Gillotti
An attractive young girl of Margaret's age, who "was thought up in Italy, but was born in America." Her long black hair and deep brown eyes coupled with the charm of her European ancestry make Dennis feel "funny" inside. He has great admiration for the fact that Gina never comes unglued in the presence of spiders, bugs or lizards, prompting Dennis to wonder, "You're lots of fun! Are you sure you're a girl?"