The Mario painting also says “Oh Mario” because the Mario painting we see isn’t actually Mario himself it is just a state of Luigi’s depression visualizing just what kind of horrific fate Mario could be going through. To BF & GF the Mario painting isn’t even there, this also partly explains why painting Mario’s note are invisible.
Real lyrics: Peppino....that is my name.... Peppino....pizza towers my game.... Peppino....that is my name.... Peppino....pizza towers my game.... Ohhhhh Gustavo......