Ubisoft is a successful company, and like all money-spinning corporations is always looking out for potential opportunities to produce hit games. There are irrepressible rumours / leaks of Mario + Rabbids: Kingdom Battle for Nintendo Switch, so it's only natural to wonder about past attempts to bring the franchises together.
Liam Robertson, well known for his work with Unseen64 and other ventures, has shared a video and some concept art from a crossover adventure game that never got past the early stages for Wii. It seems Ubisoft was keen but, at the time, Nintendo wasn't particularly interested.
There's a certain inevitability that we'll see the brands collide either today in the Ubisoft conference or in Nintendo's Spotlight / Treehouse broadcasts. We'll be live streaming and blogging on them all as they happen here on Nintendo Life.