One Got Fat is a bizarre bike safety film featuring kids with creepy ape masks. This 1963 film predates the Planet of the Apes by five years and undoubtably provided the inspiration for the sci-fi classic.
The basic bike safety message is sound: "drive your bike," signal your intentions, ride right, obey traffic rules, ensure your equipment works, use lights and reflectors in the dark, avoid the sidewalk, and don't ride with more people than the bike is designed for. This isn't your basic and boring safety film, though. The happily smug narration provided by Edward Everett Horton (of Fractured Fairy Tails) along with the pleasant music results in an interesting Twilight-Zonish disconnect while the rule-breaking children are, one by one, eliminated by road hazards, cars, and a steamroller(!). One of the Internet Archive reviewers describes the tone best. "Johnny has been crushed by a steamroller. Oh dear, what a pity, he should have used hand signals."
Download this 15-minute film from the Internet Archive and play it at your next bike advocacy meeting. I howled with laughter while watching it; my two young children, meanwhile, sat transfixed as the little monkeys all disappeared one by one.
Thank you to Cleverchimp for pointing the way to this great little film.