That means that Luigi and Donkey Kong will come visiting you for some adult fun. And if you dreamt of Koopa in the Vanilla Lake, then most probably that also means that Yoshi will do something weird to you.
GIVE ME A BREAK! It really doesn’t mean any thing if you dream about any buckle. You can dream about graves, bananas, dead people coming alive, living people going dead, people getting AIDS, people getting cancer or spondalytis or people coming f**king any thing you like – it doesn’t mean any shit. Please – actual dreams, and I mean when your brain really shows you stuff you’ve never seen – are nothing. Please do not try to interpret your dreams, they really will take you no where.
On the other hand, worst nightmares come true mostly when you repeat them verbally over and again after you’ve seen them just once. So please don’t make your life hard and just enjoy the free shows at night (playing inside your own self).