It's not! This was a question asked on Yahoo Answers and I'm not entirely convinced it's a real question. I refuse to believe that there's someone left in the world that doesn't know how to play Super Mario Bros! Here's a screenshot and link to the original question. Head over to this page if you want to play the original NES Super Mario Bros!

http://answers.yahoo.com/question/index;_ylt=AkYyfgWLg58JfNvC6OyMMJEjzKI...