Clampett attended both Glendale High and Hoover High School in Glendale, California, but dropped out of Hoover High a few months short of graduating in 1931. After he dropped out, Clampett got a job working at a doll factory owned by his aunt, Charlotte Clark. Clark was looking for an appealing item to sell and Clampett suggested Mickey Mouse due to growing popularity. Unable to find a drawing of the character anywhere, Clampett took his sketchpad to the movies and came out with several sketches. Clark was concerned with the copyright, so the two drove to the Disney studio. Walt and Roy Disney were delighted and they set up a business not far from the Disney studio. Clampett recalled his short time working for Disney: "Walt Disney himself sometimes came over in an old car to pick up the dolls; he would give them out to visitors to the studio and at sales meetings. I helped him load the dolls in the car. One time his car, loaded with Mickeys, wouldn't start, and I pushed while Walt steered until it caught, and he took off."
Clampett left Disney's studio shortly to work with Warner Bros. in 1933, where Friz Freleng hired Clampett as his assistant animator. Clampett animated for Ub Iwerks during his short tenure at Warner Bros. After Iwerks left, Leon Schlesinger offered Iwerks' directorial position to him and Clampett took the offer. Clampett began to develop their biggest star during the time Porky Pig who would compete with various Disney characters in terms of popularity.
Clampett left Warner Bros. in 1946, although it has been said that he was fired by the new executive boss, Eddie Selzer, to work on his puppet show Time for Beany. He continued to work and market on the show until his death.
Clampett died on May 2, 1984, 6 days short of his 71st birthday, of a heart attack while traveling the country to promote the Beany and Cecil franchise.