I was reading the commentaries of MGC's blog post about the NSMBU pictures and read on the commentaries, saying, the Roy Koopa artwork is the same artwork of himself on NSMBWii. Seriously?, so I open up my Photoshop to compare the two pictures and here's the result:
Result: There's no differences between the artworks.
Actually, there's a difference between the artworks.
NSMBU's Roy Koopa is mirrored! No, seriously take a good look:
http://www.mariowiki.com/Gallery:New_Super_Mario_Bros._Wii
http://www.mariowiki.com/Gallery:New_Super_Mario_Bros._U
Good Job Nintendo.
Other "great" NSMBU artworks.
Mario (NSMBU) vs. Mario (NSMB2)