I've heard a lot of people bagging on this game on the internet and even saying it's not a real Mario game because of its origins as Doki Doki Panic. I don't think it was ever released in Japan, either. But to me this IS Mario. It was the first game we had to flesh out the world and characters. And it was one of the most fun regular Nintendo games I played. I'm not sure how much from this game survived into the series, but it'll always be canon to me. I know Birdo's still around.