Ghost Writers 1958
Overview: Two writers at Paramount Cartoon Studios try to think of good stories for Casper the Friendly Ghost. They review scenes from "Casper's Spree Under The Sea," "Once Upon A Rhyme" and "To Boo Or Not To Boo." Eventually Casper himself emerges from a poster on the wall and scares the writers away. Casper explains that he thought up that gag to end the cartoon!