Watch Keep Your Grin Up (1955) Official Trailer

Casper, the Friendly Ghost, attends the circus and frightens the performers. He then encounters a Laughing Hyena that is unable to laugh. Casper, determined to make the hyena laugh, tries many tricks and none of them even sightly amuses the animal, even to the extent of grinning or chuckling. But Casper then does something that accomplishes his goal.