Ignoring Pokemon (would GF really call Pokemon merely "well known", c'mon now), the only IP they have that could apply for that description, in a pinch, is Drill Dozer.. so that can't be it either. How exciting!
I just thought of the possibility of this being a collaboration that takes form within the game's context. A well-known game that receives a Pokémon-based version as a mini-game (or larger-scale side-game) in XY. That would explain both the timing and that Moomin-Pony thing.