Normally, when you pick Chance, you are locked into the song it chooses. However, if you select the song and enter the settings menu, then back out with Triangle, you are returned to the song wheel and are no longer locked into the song chosen by Chance.
Inputting this code at the main selection screen (Dance Mode, Battle Mode, Marathon Mode, etc.) will allow you to view the developer ending after playing a round of play, without getting at least an S+ average on your songs or marathon course. A few sparkles on screen will confirm correct code entry.