Most of these drawings were made using Pencil Fantastic, a game I made when I was learning Unity in 2018-2019.
The animations were rotoscoped from reference footage using the AnimAll addon to edit the vertices of a Bézier Curve in Blender. I have a tutorial video on that subject if you're interested in making your own.
The sharp edges are achieved by quickly changing direction from forward to backward.
You can see the pencil in this one
My favorite Jeopardy contestant.
