Here's an example of something really adorable made collaboratively by two people. The first person sent the first part to the second person, who used the Doodle-on-Doodle feature to add to it and make an even cuter story out of it.

https://www.swapadoodle.com/d/5288420972691456

I think 9× is the best speed to watch it at. (I'm still thinking of adding a way for the author of a Doodle to change its default speed.)