Yeah,this happens to me all of the time,and When I change the sprite header and deleted a few sprites,mario was fine.
Wrong sprite header settings can also result to:
Mario becoming invisible (Banzai bill).
So make sure your sprite header settings are correct,or really odd things can occur.
Funniest thing I have ever seen on the IRC:
*** Adam is now known as Theythoughtmydickwasahotdog
01:28 Pikachu32 Where's a torrent of water when you need one....
01:28 AngrySun <fgt>
01:28 Narutojon1 wtf adam
01:28 Theythoughtmydickwasahotdog Th girls did
01:28 AngrySun </fgt>
01:28 *** Theythoughtmydickwasahotdog is now known as Adam.