soooo what's the HARDEST thing to animate?
i've already talked about what's the easiest thing to animate. it's fish, if you were curious. read the article to learn more! ;)
so, you're probably wondering, what's the opposite? what's the HARDEST thing to animate? well, in the aforementioned blog post, i mentioned the bouncing ball. today, i'm here to tell you that that is the hardest thing to animate.

image from animation apprentice
take a close look at the space between each frame of the ball. for a bouncing ball, or anything in motion, to look natural, it has to ease in and out. you have to smear the image during faster movements; that's squash-and-stretch. you have to use proper spacing. if you don't do that, the movement of the object will look stiff and robotic. kinda like this ball:

image from wikipedia
so, to any aspiring animators, heed this important advice, and remember the squash-and-stretch method! animation is all about making objects move, so make sure they move properly.