This is based on a little talk I gave to students during a one-week animation crash course at Cambridge a few months ago. The project was to create a character and animate it performing a simple looping dance. I first briefed them on the very beginnings of the process, looking at reference and collecting research materials to inform their creative choices, and explained and demonstrated the basic tools they needed to use, including keyframing, in-betweening, and timing. Then I showed them this clip from Princess Tutu on the morning before they actually started drawing their animations.
I used this bit in particular because I thought it was a really accessible way to demonstrate a key difference between communicating with moving image compared to still image. While many of the same principles apply (in particular, to your keyframes, which I’d already done my best to drum into them), the in-betweens can carry a lot of weight and really change how the action reads.