Just wanted to clarify some rules before I attempt stuff in a run, to make sure it’s okay.

I was thinking of maybe trying to do a little bit of testing about whether having temporary player 2 could maybe save time in an Any% run. Is using 2 players allowed in Any%, or just Co-Op?

Also, I assume a 2nd player is required to be permanently in the game for a valid co-op run, but that technically isn’t specified in the rules. So did I assume correctly?

You've got a good point in that we do not have a rule about this right now. I would say that the use of a second player of any kind qualifies the run as Co-Op, so even a temporary partner would disqualify a run from Any%. Since we don't have a rule on that though, and I'm not a mod, I do think we should have a discussion on this to make it more clear

I just submitted a co-op run today so it isn't verified yet, but we use a new skip that is only possible with two players. Personally I feel like the spirit of Any% in general, regardless of what game it is, should be to create the fastest possible completion of the game, and If that includes a player 2, then I feel like that should be allowed.

That's my opinion at least.

2 player mode is also only on the console versions as far as I'm aware, and recently PC and console were split on the leaderboard, so that specific part of this issue is kinda already solved?

What if one player were to control both controllers? Would the cutscene skip be allowed in an Any% run?