First off, forgive me if this has been done before. I know full-game playthroughs aren't new per se, (RTW stream is coming to mind) but I just got this thought the other day of a 2-person (or more, I suppose) Lem-off. Basically, both players get on a skype call and begin playing at the same time on the same port, and whoever completes the game first wins. (I'd suggest just using the Lemmini version, but I suppose any could work.)
I understand this might be logistically difficult to stream on Twitch or similar, due to the multiple-screens thing, but I'm betting that could somehow be worked out. Another possibility that occurred to me is just opening it up to an en masse Skype call, thus allowing for as many participants as possible.
The other potential issue coming to mind is timing, as the world is rather large and contains many time zones,
but again, I suspect this could be worked out.
Just thought I'd float this idea and see if anyone found it interesting. Open to any and all questions, concerns, criticisms, or propositions.
Take good care of my Lemmings!
-Hyp