Head over to the vent ramp and participate in a big air contest with Scooby Doo.
Start Scooby's motion until he can get off the ramp and when he is airborne, increase his speed and height, so is his downward speed. Repeat the steps to jump higher and higher. Your sense of coordination will help Scooby do the big air. Start rolling!

Left / Right Arrow Keys - To start his motion while on ramp.
Up Arrow Key - To increase his speed and height while going upward.
Down Arrow Key - To increase his downward speed.