Did you ever draw stick figure flip books in your school notebooks? I used to get a kick out of it. It was something fun to pass the time when I probably should’ve been paying attention in class.
Recently I found this app Animatic. And it captures so perfectly that old feeling of flip book animation. You draw (on your phone or tablet) frame by frame, and it has onion skinning, which is basically semi-transparent images of previous frames for referencing. You can also adjust frame rate of the overall piece (if you get the subscription for 9.99 a year you can adjust frame rate per frame as well). You can also link it to PhotoShop to get your frames onto your desktop.
What I love about it is it took a nostalgic pastime of mine, and made it much easier to do. And the price of entry for the app is FREE, and that free version is perfectly useful as it is.