Rubberface (1981)

This film was shot in Canada and released there as, "Introducing...Janet." Janet is an overweight girl who has a knack for making the other children in school laugh...by making fun of her own weight. In seeing the other kids' reaction, she feels that she might have a career as a comedian. She visits the local comedy club, where she finds Tony Moroni, a struggling comedian whose jokes often fail. Together, Tony helps Janet build self-esteem and she helps him with his material.