The more we talk about, the better it sounds.It wouldn't even be taken seriously either.
I can just imagine as things start to look grim for the mushroom kingdom, suddenly, out of nowhere, Waluigi would come driving in on his Go-kart and rams it into the Origami King killing him instantly. Then, with the mushroom kingdom free from the King's rule, he leaves as quickly as he came.
He just shows up and then fucks off. And then... AND THEN!!!! FUCK HERE IT IS. And then they would have to put him in Smash for real guys.