Everyone should be happy. (Final roster topic)

[Koopaul]

There isn't, aside from a few cameo appearances, or in "noncanon" games like Mario Sports. And even then that's not a connection with Mario, that's a connection with Nintendo

Those aren't cameos, as in Samus taking a nap in Mario RPG. He was a part of the cast and crew. A cast that is made up entirely of Mario-only characters implying that in some sort of way Diddy is a Mario character... sorta. I mean its quite obvious that Nintendo believes this to be so. Look. The connection IS there. Nintendo considers Diddy to be somewhat a part of the greater Mario cast. Even more so than Wario characters!

K. Rool and Kremlings are even featured in the Mario Sports games, and maybe you can argue if its canon or not, you cannot deny that DK elements are so strong in Mario games it would be ridiculous to overlook it.

So yeah...

I mean if you are that critical on if canon means something, than that means Waluigi doesn't exist.