This is something I kinda came up with, but I'm sure many people already started this, (mainly with traditional media in classes)

Rules:

You are only allowed 5 minutes to draw out a scene.
Scene is chosen randomly via friend or acquaintance.
Share via Livestream or some other method (I prefer JoinMe).
Watch at how your poses improve.

I recommend that you actually do it with a person watching. It is not only easy to lose track of time, but the other person can actually help you with instant criticism.

The challenge is a great way for anyone to just draw something.. and if its not going well... just wait til your 5 minutes are over.. and try again :3