So something I've been wondering for a while now;

How in Wi-fi does one hold up sleep clause when the sleeping poke may have natural cure ( ) and switches out.

Do you ask your opponent what ability it carries if you can talk to them? (somewhat unfair to the user as it reveals strategy)
Assume it's asleep until it comes back in? so sleep clause is "held" even though the opponent has no asleep poke.
Assume it was cured and sleep something else. (which may break sleep clause)

...

I don't think I've ever seriously looked at those in a battle before, (feels stupid)

Not a whole lot of people do, I know I didn't use to do that, I only started doing that only a few months ago.

Yeah, I never realized that either and have actually been wondering that too. So thanks, tji, for your help. Now, it's story time; one time I got in a Wi-Fi battle with someone, and we went by the Item clause, Species clause, and of course Sleep clause. He statred off with a Gengar and proceeded to put EVERYONE OF MY POKEMON to sleep. He thought that's what sleep clause meant; that you had to put all your opponents to sleep before you could do anything else, and I was just like, "WTH, man?" Ah, n00bs...