It depends on your definition of "beatable," really, since you never face Bowser, but there is a way to skip to the credits sequence of Super Mario World in five minutes if you can execute a precise mutli-step process that initiates a glitch.
Until recently this glitch was so involved that it had only been done in tool-assisted speedruns, but the human desire to push further knows no boundaries, and someone has now done it on an actual SNES with raw will. Twitch streamer Minecraft SethBling...
