Rats on the ice!
Florida Panthers fans were responsible for two delay of game penalties against their team last night because they refused to stop throwing toy rats on the ice after goals. You're probably too young to remember, but this is a thing Panthers fans used to do back in 1996, when the Panthers advanced all the way to the Stanley Cup Finals. Legend has it that the tradition started when winger Scott Mellanby killed a rat with his stick in the locker room and then scored two goals.
Baseball drone training
Back in 1985 — long before internet pranks — Sports Illustrated pulled a classic April Fools' Day gag when they published "The Curious Case of Sidd Finch." According to the story, from George Plimpton, the Mets were trying out a pitcher who could throw the ball 168 mph, played the French horn, and had studied in Tibet. Believe it or not, many people were fooled.