Near the end of the game you get to see these cosplaying mid-bosses as a surprise. Obviously based on Wario and Waluigi. I did smirk at the parody.
You actually have to fight them twice. The first time I easily noticed that Bwario played almost exactly like a valkyrie enemy and Bwaluigi was like a smasher.
Then they team up with a villian known as the Lava Queen. It was a pretty tense fight, but I didn't have to start over so I was glad there.