Boy Meets Girl.

Two lazy screenwriters need a story for the studio's cowboy star. A studio waitress turns out to be pregnant. This gives them the idea for a movie about a cowboy and a baby. The waitress's baby becomes the star. The cowboy and his agent run off with the waitress and her valuable asset. The writers retaliate by hiring an unemployed extra to impersonate the baby's father. But the extra already knows the waitress...