Game dev exquisite corpse:

Each person gets one week to do or add whatever: graphics, music, code (although you're discouraged from rewriting all the code others have written even if it's dumb) and then you send it off to the next person without comment.

You could all keep your own changelogs that can be added to one another afterwards to see who did what.

Keep on going in cycles until you've all cobbled something together.

Then send it to the wide world, or at least to me~