hey, I'm glad you enjoyed my video. there's a thread about the name entry glitch somewhere but I'm too lazy to find it, so here's the basics of how it works. the glitch is executed by exiting the character select screen and entering the name entry screen at the same time.
here's the method:
1. erase all the names on your memory card except for one
2. select your character
3. hover the cursor over your character's name (where you enter names)
4. press A and B at the same time, continue to hold B
5. right as you would have exited the character select screen, press A
if you timed it correctly, you should be at the stage select screen and you can play with just one character on the stage.
here's a time saving trick if you mess up a lot. after you select your character, press L+R+Start to exit back to the main menu. this will save the character you chose so each time you mess up and go back to the character select screen, you don't have to re-select your character.