You remember Karnov, right? The muscular fire-breathing circus strongman? He has his very own NES game, and it's actually pretty tough. Tough enough that if you make any kind of progress that you might not want to turn off your NES when you're done because you'll have to start over from Stage 1 if you do.

Or do you?

If you go to the title screen

And on Controller 1 hold Right + Select + A + B, and while holding all those down, press A on Controller 2 one time for each stage you want to skip, and while still holding down all those buttons on Controller 1, hit Start on Controller 1 (you might want to enlist the help of another hand or a foot).

Done right, you'll be whisked away to the stage of your choice

The only problem is that you won't have the benefit of having collected the items scattered around the levels that you skipped, but that's a small price to pay, right?