Finally made it to the end of the Mario bootleg "Syobon Action's" level, and thus you see an uncanny white cat with a smiling face.

"...NOW HIS BODY SHALL ETERNALLY REST IN THE SEA, ALONG WITH HIS WAXED WINGS."

After he says that line, he grew and darkened. Turning into a giant, monstrous, muscular shadowy cat creature.

"BRAVERY SHALLN'T COME TO RESCUE ANYMORE, FOR YOUR PETRIFY IS WHAT I SENSE."

He looked at you with a twisted sense of hunger in his face.