Has something happened to your game? The cartridge may be tampered with, or it could be corrupted from old age/misuse.
Oh, and missingno. technically isn't supposed to appear anywhere, but...yeah. <img src='http://www.cavestory.org/forums/public/style_emoticons/<#EMO_DIR#>/tongue2.gif' class='bbc_emoticon' alt=':p' />
I can't even D: D: D: