By today's standards, "Mr. Peepers" was improbably gentle. Whereas contemporary TV comedy is dominated by wisecracking urbanites, this 50s hit, set in small-town America, rarely featured actual jokes. At Cox's insistence, the show also eschewed broad physical gags and belly laughs in favor of gentle character comedy and smiles. The show derived humor from slight exaggerations of mundane situations. As for the central character, comedian Steve Allen has observed "He is the mouse in us all; we want to protect him and feel tender toward him."

Prior to that career transforming success, Cox had supported his sister and partially paralyzed mother (Eleanor Frances Atkinson, aka mystery writer Eleanor Blake) in NYC by working variously as a shoe-weaver, puppeteer apprentice, dance instructor (he taught the Lindy Hop at a dance school for $1.50 a lesson) and silversmith. He and Marlon Brando had been friends since childhood and the pair shared a Greenwich Village apartment. Cox used to amuse his friends at parties by performing character monologues inspired by people he had met. Under the influence of Brando and other theatrical folk, Cox became affiliated with the American Creative Theater Group where the director urged him to shape his monologues into a nightclub act. Cox auditioned for Max Gordon, owner of the Village Vanguard, a legendary Greenwich Village nightclub, and made his professional debut the same night in December 1948. That initial one evening engagement extended into months. Cox's career as a hip downtown comic had begun.

Cox delivered his monologues in a quiet, droll manner. His characters tended to be small, unassuming people who earnestly shared all the intricate if banal details of their lives. Cox soon took his act uptown to more posh venues where he caught the eye of a theatrical producer who cast him in the Broadway musical revue "Dance Me A Song" in early 1950. The show received lukewarm reviews but Cox won raves. By the end of the run, he was sorting through more than 20 offers for work in film, TV, theater and clubs. Cox's stock grew as he played the Plaza Hotel's Persian Room and appeared on numerous TV and radio shows headlined by Perry Como, Ed Sullivan, Garry Moore and Arthur Godfrey. He even hosted his own NYC radio show over WNEW in October 1951. That same year, Cox segued decisively to TV with a starring role as a mild-mannered trouble-prone policeman in NBC's "Philco Television Playhouse" production of David Swift's "The Copper". The success of this outing with public and press alike inspired producer Fred Coe to develop a sitcom pilot for the unusual performer. Little did they realize that Cox would basically play variations on Mr. Peepers for the rest of his career.

After his sitcom succumbed to the overwhelming popularity of "The Jack Benny Show", Cox returned to nightclub work and TV guest shots in series and specials. A follow-up sitcom, "The Adventures of Hiram Holiday" (NBC, 1956-57), failed after just four months but in 1958 NBC signed Cox to an unusual seven-year, $50,000-a-year contract to develop special projects for the network. Not much came of this opportunity but Cox managed to write a play, ("Moonbirds" which closed after three performances) and several books.

Cox made his film debut as a comic character actor in the poorly received musical remake "State Fair" (1962). He won the best notices as a competition judge who gets pickled from eating too much brandy-spiked mincemeat. That same year, he acted with Marilyn Monroe and Dean Martin in the uncompleted George Cukor-directed comedy "Something's Got to Give". Cox played a shoe store clerk whom Monroe attempts to pass off as her desert island partner. He returned to the bottle in "Spencer's Mountain" (1963) as a young reverend whom a free-thinking Henry Fonda gets drunk on his first day in town. Cox continued to prove himself adept in feature ensemble work in the air crash mystery "Fate Is the Hunter" (1964), the comedy anthologies "The Yellow Rolls-Royce" (also 1964) and "A Guide For the Married Man" (1967). He provided tragi-comic support as dedicated sonarman Merlin Queffle in the seagoing military drama "The Bedford Incident" (1965). Cox worked with his old pal Brando playing a doctor in the WWII drama "Morituri" (also 1965). Beginning with the lackluster Disney period musical comedy "The One and Only, Genuine, Original Family Band" (1968), Cox began appearing primarily in broad family comedies. He garnered many laughs in "The Barefoot Executive" as the stooge of a desperate TV programmer (Joe Flynn) and as a playboy "sailor" who never leaves dock (he replaced the engine with a wine cellar) in "The Boatniks" (both 1970).

Back on TV, Cox found a new young audience as the voice of the superheroic canine "Underdog" (NBC, 1964-66; CBS, 1966-67; NBC, 1968-73) and his humble, lovable alter-ego Shoeshine Boy on the popular children's cartoon from producer Jay Ward. Viewers became reacquainted with his mousy features and low-key witticisms as the panelist in the upper left "square" from 1966-73 on the game show "Hollywood Squares". He also represented Jockey Shorts ("Outside I might look like Wally Cox, but inside, I feel like Tyrone Power") in a series of commercials. Sadly, his greatest TV work "Mr. Peepers" is all but lost to younger viewers as they were broadcast live and few kinescopes survive.

When Cox died in Bel Air from a heart attack at age 48 in 1973, his loyal friend Brando flew in from Tahiti to handle the cremation.