Here we were going crazy over Mario's nipples, and now we have something like this! Apparently during 1988-89, Nintendo had partnered up with manga publisher Kodansha for a series of comics. Each one focused on a particular game in the Mario series at that point, and the one we're looking at here tackles Super Mario Land.
In this particular issue, a Fish Bone jumps out of the water and bites Mario's butt. This causes Mario to yelp in pain and launch right out of his overalls, leaving his twig and berries for all to see. You can bet we're never going to see an officially-licensed bit of merch that shows this kind of thing again! You can see the uncensored version after the jump.