Well, I guess hell has finally frozen over.
Sure, fifteen years ago, this never ever would’ve happened — but that’s not the point! Sonic and Mario can now beat the snot out of each other. Official SSBB website Smash Bros. DOJO!! has posted a few screenshots if moving images aren’t your thing.
Now Mario and Sonic can have it out once and for all. 
Back in 93, no way in hell this would ever happen. Check it, including some video! (Thanks, Jon!)