https://www.polygon.com/2017/8/29/16220766/mario-rabbids-kingdom-battle-intro-cutscene

Mario + Rabbids Kingdom Battle is a surprising success, according to critics, and it proves that from the very start. The game has one heck of an involved intro that’s sweet in several ways — and shows who the most important person in Mario’s life really is.

There’s a lot going on in this six-minute cutscene, lorewise. It turns out that a Super Mario-obsessed young scientist is the culprit for combining the Rabbids’ world and Mushroom Kingdom, after her inventions go awry and open up a major wormhole that sucks up Mario and the crew.