A hat trampoline[1] is a beige bouncy pad appearing in Super Mario Odyssey. Though Mario can bounce on them normally, he can gain much greater height if bouncing on them as a T-Rex.
Three hat trampolines are found in the game, all of which are in the Cascade Kingdom. The first hat trampoline is located near the Crazy Cap shop closest to where the "Our First Power Moon" Power Moon is located. The remaining two hat trampolines are found in the Dinosaur Nest area; one of them is at the ground level where the "Dinosaur Nest: Big Cleanup!" Power Moon is found, and the other is further below, and must be utilized to obtain the "Dinosaur Nest: Running Wild!" Power Moon.