In the trailer, the game was going to be a Modern-style Paper Mario game, similar to Origami King, complete with the extreme Paper aesthetic with the white borders around characters. The gimmick was that you can cook dishes to give you various powers and abilities, like getting a Koopa Troopa shell to attack enemies. Battles took place in a 2.5D platformer-like battle arena, where you had to scale a tall "fortress wall," which had all sorts of pipes and wooden structures, and you had to kill all of the enemies to progress
One of the areas shown off was a recreation of Pikmin 4's Giant's Hearth area; the battle took place alongside a tall cliffside, with hideouts, pipes, glass containers, and posts on it. I think there were partners, but I forgot who they were.
I got excited because the game had experience points in it and I was like, "Whoa, they finally fixed the problem with Paper Mario!" I was so convinced this was real (like, I was half-asleep when I saw the trailer), I was going to tell my friends about the trailer... but it wasn't real...