https://www.gamespot.com/articles/super-smash-bros-ultimate-limited-edition-comes-wi/1100-6461031/

We got a whole lot of new information in the latest Super Smash Bros. Ultimate-focused Nintendo Direct presentation. Among the announcements was that when the game launches on December 7, it will be available in a bundle called Super Smash Bros. Ultimate Limited Edition. This version comes with the game itself, plus a Smash-branded GameCube controller and a USB adapter that lets players connect up to four GameCube controllers to their Switch. So far this bundle has only been announced for Europe, though it may come to the US as well.

A GameCube controller has been the preferred input for pro-level and diehard Smash Bros. players ever since Super Smash Bros. Melee came out for GameCube in 2001. Each main Nintendo console since then has supported the controller, as have all non-handheld installments of the Smash Bros. series.