First film based on an advertisement

The character Ernest P. Worrell, played by actor Jim Varney (USA), was originally created by US advertising agency Carden and Cherry in 1980.
He proved extremely popular and a spin-off television series, Hey Vern, It’s Ernest!, was subsequently produced. Ernest’s first movie, Dr. Otto and the Riddle of the Gloom Beam, was released in 1986, and he went on to star in a further nine productions.