In 1978, Howerd appeared in the big-budget Hollywood musical "Sgt. Pepper's Lonely Hearts Club Band" playing Mean Mr Mustard, acting alongside musical and film talent such as Peter Frampton, the Bee Gees, George Burns, Alice Cooper, Aerosmith and Steve Martin. He was cast by producer Robert Stigwood as he was on Stigwood's record label at the time. The film was a critical and commercial flop. Since Howerd was not well known to American audiences, this may have been his biggest exposure in the US.