There are a few ways to create squash and stretch in After Effects, some more complicated than others. Here, Mikey Borup busts out a little used effect in After Effects, the Warp Effect to create squash and stretch. Ae’s warp is similar to its sister effects in Illustrator, which will allow you to apply a deformation envelope to a selection.
Mikey uses the Ae Warp effect as a quick way to create squash and stretch, and also shows how to create some simple expressions to drive it while leaving the main layer’s transform value keyframes free to be further animated.
School of motion had a detailed look at creating squash and stretch in After Effects in a pragmatic setting showing development while creating an animation.
