I've long held that Nintendo is pretty much the Disney of video games, and that the incredible attention to detail put in games like Smash Bros. proves it. So really, a Smash x Disney mash-up is a match made in Final Destination.
The Mickey x Mario combo you see above is the handiwork of Michael Villamejor. Isn't it perfect? The faces of Nintendo and Disney, blended together. The rest of Villamejor's Smash roster is similarly amazing:
Goofy x Luigi
Pikachu x Stich
Russel x Ness
Pete x Bowser
Olaf x Kirby
Peter Pan x Link
You can check out more of Villamejor's work here, including the rest of his Smash mashups. Or, if you'd like, you can check out his Disney Princesses x Street Fighter characters mash-up -- that's pretty excellent too.