Super Mario Bros. Wii Leaked

[Vipershark]

Wario and Waluigi wouldn't make sense as they're both villains. Sure Wario helped out in Super Mario 64 DS, but only because of his weakness to greed and Bowser ticking him off. Waluigi hasn't done anything major in a main Mario game, but he's the type that wants to annoy the side of good. For example, he'd rather give them a good booting and then laugh like a douchebag.

The only time I could see Waluigi working in a main Mario game is as a villain (the mini-boss kind or the henchman if you will).

technically wario isn't bad, he's just greedy and doesn't care what the good guys do
in his more recent games, he's always fighting bad guys to get his money

he'll actually help the good guys without question if it gets him a good payout