Two episodes from the Arthur television series, based on the Arthur Adventure Books by Marc Brown.
Arthur writes a story -- Locked in the library!
(First story) Arthur, struggling with a school writing assignment, decides that all he needs is a little imagination to make life sound more interesting than it really is, but he crosses the line when the story of how he got his puppy starts to involve invisible elephants and trips to outer space. (Second story) If only Arthur hadn't called Francine a marshmallow! Now they're locked together inside the library and they either have to make up or face the long, scary night alone.