Watch the episode "Stimpy's Big Day"(the episode where Stimpy gets to host the "Gritty Kitty" commercial). Stimpy asks a horse to sample two cat litter products one the Gritty Kitty and the other an ordinary product. After the horse tests them both he tells the audience that sample A(which is Gritty Kitty) is surely the better product. But if you look at the box the horse is holding up the letter B is written on it. After a few seconds it will suddenly change back to A so you must be quick