In 2011, after spending years at each other’s throats, former "Real World: Key West" housemates Johnny and Tyler proved some hatchets were designed to be buried and pulled out a "Challenge" win with only each other as teammates.

The game’s resident oil and water, Emily and Paula, merged their discordant methods of game play two years later to earn a pair of gold medals for their two-woman ensemble. They'd each have initially preferred to work with cadavers but soon proved adversarial pasts didn’t necessarily dictate contentious futures.

When the "Challenge" returns for Season 28, it'll ask a familiar question: When foes are forced to work together, will they fall apart at the seams or allow resentments to fall to the wayside? Either way, the forthcoming "Rivals III" cast is in for a sizable headache: For the first time, same-sex solidarity is out the window, and man-woman antagonists will fight for first-place. So long, gender divide…

Yes, "Exes" proved guys and gals could work together, and some "Bloodlines" teams transcended genomes. But you can rest assured "Rivals III" won’t work so seamlessly, and while we can’t say much, trust this: The next crop of opposite-sex teams is going to bring the fireworks.

Check out the promo for the next "Challenge" Mexico-based season above, and hang tight for "Rivals III," which will premiere later this year!