Performing the Glitch
The glitch can be performed by using the following method:
Enter melee mode. In custom rules, select stock mode and set the number of stocks to whatever you choose. Select one and only one character. Then perform the glitch as follows: Hover your cursor over the name field, and press A and B simultaneously. Then release A, but hold onto B. Scroll down to "Name Entry." Press A at the right time whilst still holding B. If you timed it right, you will go to the Stage Select screen. Select your stage.
If you performed the glitch, and the game does not freeze, the melee should end as soon as the announcer says, "Go!"
A melee with only one character is impossible under normal scenarios. However, since the Name Entry glitch forces the game to advance, all opposing stock has already been depleted at the start of the battle and you win instantly.