spotted what could be such a creature this week via Germany's rating board, and its name is Giana Sisters vs. Super Meat Boy (or feminus gianicus meat-boyicus in science-speak).
While a Super Meat Boy / Giana Sisters crossover has yet to be officially announced, the rating board has a fair amount of information attached to its rating; the listing claims that Giana Sisters vs. Super Meat Boy will be a PC title, published by Headup Games. We've provided a screenshot above, but you can see the listing for yourself by checking out the board's website and searching "Giana Sisters vs. Super Meat Boy."
Super Meat Boy and Giana Sisters: Twisted Dreams are both independently-developed 2D platformers, so a team-up isn't exactly out of the question. Still, it's an ... unexpected team-up to say the least.