A while ago, I had this thought for a collaborative comic strip that I want to do. I'm not under the impression that it's a completely original idea, but I do think it would be a fun way for a couple people who like to draw to spend an evening... and to have something to show for it. The concept is very simple, and only requires four people and drawings utensils, though I can imagine a pub and/or a few beers would help :)
The core of this idea is the old three-panel comic strips you see in newspapers, the kind that usually ends in a gag and have no real continuity day to day. Get four people around a table with four pages of paper, each page already divided up into three panels. Each person draws some scene or scenario in the first panel, and when completed, passes their page to the person on their right. Then, they'll have to draw the second panel of the comic strip they were handed, and upon completing it, pass that page to the person on their right. Then they'll have to complete the third and final panel of the strip they were handed, again passing that page to the person on their right.
Having done so, each participant should have drawn three times, three panels for three different strips, and have in front of the a completed three-panel comic that they did not draw. In this last phase, they are responsible for adding word bubbles and dialogue to this last strip, trying to make a sensible story or gag out of a strip they have not seen that night at all.
When the process is completed, the people at the table should have four comic strips that they all worked on. It would probably be interesting to have everyone draw and write willy-nilly, but I think I would prefer some base ideas set, so everyone is doing four strips of the same comic. For example, everyone agrees on the settings, the characters, the name of the strip, and the basic idea.
I would love to rope in a couple creative people to do this, and afterwards inking and scanning and uploading the strips. If it's enough fun, our little comic might have to become a regular thing :P