World Star-5 (New Super Mario Bros. 2)
From the Super Mario Wiki
World Star-5 is the fifth level of World Star, in New Super Mario Bros. 2. This level combines the elements of grass and sky. Lakitus appear alongside red and green Koopas and Paratroopas. The level also contains a Gold Ring and Dropping platforms.
To do the trick, the player must use a Lakitu's cloud. While riding the cloud, the player must move to the Koopa Troopa (with ? blocks on each side) and stomp on the Koopa, then kick it. Repeating this enough times, will grant Mario and Luigi unlimited 1UPs.