http://www.ign.com/articles/2013/08/21/wonderful-101-almost-had-all-star-nintendo-characters

Once upon a time, Nintendo characters nearly starred in Platinum Games' The Wonderful 101, according to designer Hideki Kamiya.

"Originally I got an order from the president of Platinum Games, Tatsuya Minami, asking me to create a game idea that had an all-star cast of Nintendo characters plus characters from other games and that's how the project started," Kamiya told VideoGamer. "I thought how I could satisfy everyone and make everyone happy and I came up with the idea of why not having everyone displayed in the game at the same time. That's where the idea was born."

That plan changed following that project getting paused, and by the time Kamiya returned, the idea changed.