There are 20! / (5!)^4 = 11,732,745,024 ways to select characters for an All Levels run of this game such that each character is selected the same number of times. I also added my own restrictions that no two consecutive levels can be played with the same character, and the run shall begin and end with the best character (Toad). This made for an interesting character-selection route, which can be represented by the following quaternary string of length 20: "20312103023131020312" where 0 = Mario, 1 = Luigi, 2 = Toad, and 3 = Princess. Emulator used: Nestopia v1.40