Hammer Brothers...
Assuming you've been kind-hearted enough to be rescuing Toad every time he needs it up to now, you should be rescuing him (once again) from an evil turtle with a big hammer! If you're very cruel and have been leaving Toad to fend for his poor fungus-headed self, you'll be facing down the same evil turtle with the same big hammer, only you won't be rescuing anyone, dig?  Give the brothers a jump each at the start, then stick to your punch. Use mushrooms if you need 'em! When you're down to just one brother and he 'Valors Up', jump him again and that should be the last of him. You'll win one of their schway hammers for your own personal use in the future.  A new way to cause destruction?  Count us in!