Originally Posted by limitufc
Or is that an impossibility?
I don't see how it is as it already has happened.
Chuck Liddel from the UFC (wearing a UFC t-shirt to the ring) entered the Pride 2003 Middleweight Grand Prix tournament. He defeated Overeem in the first round and then got clobbered by Rampage (Chuck's corner threw in the towel).
UFC fighter vs. Pride Fighter. 2 major competing organizations. Happened in 2003.