As it was already heard, at least some runners are interested in running this game in the same manner as CnD2 that is 1 player 2 controllers. It seems like valid additional category with some strats and skips still being possible to be executed in the similar way as standard coop (like flying with balloons in Zone I) and some need to be adjusted.
Furthermore, the rule saying that 2 chipmunks need to be present through the whole run will stay with small change, that you can kill off chipmunk in bonus section to have it back with full lives in next zone, if it's needed. In my opinion, it will help in some situations and both chimpunks are still there, when you play through zones. Additionally, similar rule as in CnD2 will be added "Due to the nature of the run, it is strongly recommended to stream live attempts, possibly with a webcam that shows the setup you're using to play 1 player 2 controllers." , since it's quite easy to cheat in this category just having someone else sometimes pressing buttons on second controller.
Lastly, I'm not sure how to treat current two runs in coop with "No One" describtion. Technically, second person is not playing, but second controller is not used as well in those. However, I would lean more towards moving them to new category, since they fit it a little bit better.
If there are no major objections from runners, new category will be implemented in few days in a shape as described.

Excellent information shared on this! Thank you for your diligence and I hope the community is excited like they have been about previous categories and challenges to date. Great work hirexen.

Great news, I'll have to take a look at these runs!

My take on the 2 runs with "no one" could stay where they are since the controller is not used. Maybe add a description to explain what is happening. It kinda belong in this category as "history" of 2 players runs.

For now, empty category "Any% (1p2c)" was added to miscellaneous with mentioned rules and we will see how it develops. I see it being potentially close to any% time, so it can be moved later from "miscellaneous" to standard ones. Additonally, I agree and can leave the runs with "no one" in normal coop now, which were using just one controller.