Ubisoft just shared a story trailer for Mario + Rabbids: Sparks of Hope, going into a bit more detail on the game's setup and plot. More importantly, there are a few big hints within the trailer that the game's main villain, known as Cursa, is actually a possessed Rosalina.
Back when Sparks of Hope was first revealed, Mario fans were quick to point out the addition of Rosalina Rabbid, with many hoping that it also meant that Rosalina herself would be in the game somehow. Well, in a real monkey's paw scenario, it looks like those fans have got their wish - although in a much darker way than they might have anticipated.
The latest trailer for Sparks of Hope shows the rise of the Darkmess and the main villain behind it all - Cursa. Only, Cursa looks a little familiar thanks to the design of her outfit, her relationship to the Sparks, and the singular eye that can be seen. Cursa's outfit is very reminiscent of Rosalina, looking like a cosmic dress of sorts. We also see that she hesitates to crush the Sparks, this game's combination of Rabbids and Lumas, implying that she has some sort of relationship with them.
Those two factors were already enough to hint that Cursa is actually Rosalina, but the final piece of the puzzle makes it all but certain. Cursa's design has only one of her eyes showing at all times, which is a clear reference to how Rosalina's hair always covers one of eyes and only lets you see the right eye. To make it even more obvious, we actually see Cursa's eye turn blue at one point in the trailer when she's looking at the Sparks, matching Rosalina's eye.
If you somehow aren't on the Cursa is Rosalina train by now, we also see the villain conjure up a massive galaxy hand that resembles Cosmic Spirit Rosalina from Super Mario Galaxy 2. All of these factors combined make it pretty clear that Rosalina has somehow found her way over to the dark side, although how that's happened has yet to be revealed.