If you scour the Internet for lost games as much as I do then you've probably at least heard of the All Night Nippon version of Super Mario Bros. by now. Basically, once upon a time Nintendo gave the original Super Mario Bros. an All Night Nippon makeover, Nippon being the popular 1980s overnight Japanese radio show. This edition of the game takes levels from both the original Super Mario and the "Lost Levels" sequel and swaps out some of the game's many enemies for characterizations of Nippon radio personalities. Don't try to make too much sense of it. Coin Heaven explains it better than I can.
Some levels are more-or-less like the original. Level 1-1 plays fairly familiarly, with the most immediately noticeable changes being cosmetic. It's night — All Night Nippon, after all — and the background sprites are from the Lost Levels. In short, Nintendo slapped a face on anything they could. For those only familiar with the regular Super Mario Bros., the items will seem strangely placed.
Strange, eh? It seems unusual to see a ROM hack come from Nintendo itself, especially one that integrates material from a then-popular radio show. I can't imagine Nintendo of America doing such a thing here back in the 1980s. Maybe it's just as well. I don't think the world is ready for the Who's The Boss? version of The Legend of Zelda.