If you have access to it, go to Route 18 and find the house with Inver in it. He'll challenge you to an Inverse Battle. What happens is super-effective moves and not-very-effective moves are swapped. You have to completely reverse your strategies and use Pokémon that would otherwise be poorly-equipped for the situation.

It's seriously awesome, and you can battle the guy once every day. It's just a pity they didn't expand much on the concept. Check it out!

All I can think of after reading that is Weird Al.

This is a fun gimmick that needs more attention. Needs more battle facility and Wi-Fi.

If only there was some kind of plot point in the story that makes every battle after said plot point, but before finishing the climax of the story Inversions.

That'd trip people up real good.

I dunno. Then it'd just be your regular competitive play except with different movesets and stuff. I'd say this would be better as a move like Trick Room. Maybe last like 3 turns.

Ooh, having a move that inverts effectiveness would be pretty cool.

A five turn "Inverse Room" move would be very fun to play with, indeed. I can just imagine all the grass types...
But that would also make Ferrothorn pretty useless, so that idea scares me, too...

^ Well, that's why I kind of thought 3 turns would be ok. Same as Trick Room, it can be reversed if the move is used again. I was kinda hoping they'd make a move where Atk and Sp Atk would be inverted since I'm sure stuff like Tyranitar, Gyarados and others would enjoy it due to their *movepool.