Just press the green flag. Here is the Luigi version of the same spritesheet: https://scratch.mit.edu/projects/71611596/
I went and downloaded this sprite sheet: http://www.smbhq.com/users/sprite/smb_spritesheet.gif and then selected the 6th row on the Mario side of the image on Scratch. Please download the sprite sheet linked here and remix this project to make it better!!!!!! UPDATE: (Jul 27 2015): -Added SMB Overworld Theme mp3
