Cartoony Prank

What happens here is hard to explain. A thief steals a bag near a prank victim and a high speed chase ensues. While a police officer is running after the thief, they stumble onto a Scooby Doo movie set and do the whole "people running after one another and coming in and out of different doors routine" - to the amusement of the prank victims watching on. But how can the thief and cop be running in and out of the doors and hallways so quickly? It's revealed that the prank victims are actually seeing double - there are two twin policemen, and the thieves are also twins. All four of them have been running all over the place, adding to the confusion!