SSB64 Matchups

SSB64 has 12 characters
144 2-character matchups
1728 3-character matchups
20736 4-character matchups

22608 possible character combinations in total

1 of the characters has 6 costumes (Captain Falcon)
4 of the characters have 5 costumes (Donkey Kong, Kirby, Mario, Samus)
7 of the characters have 4 costumes (Fox, Jigglypuff, Link, Luigi, Ness, Pikachu, and Yoshi*)

6 + 4 * 5 + 7 * 4 = 54 unique costumes in the game

Combinations of 2 costumes: 54 * 53 = 2,862
Combinations of 3 costumes: 54 * 53 * 52 = 148,824
Combinations of 4 costumes: 54 * 53 * 52 * 51 = 7,590,024
In total: 7,741,710 possible matchups so far

Three teams: Red, Green and Blue (henceforth R, G, and B)

Combinations for teams and characters in a 2-player match: 3 * 144 = 432
(combinations are RG, RB, GB)
Combinations for teams and characters in a 3-player match: 7 * 1728 = 12096
(combinations are RRG, RRB, GGR, GGB, BBR, BBG)
Combinations for teams and characters in a 4-player match: 12 * 20736 = 248832
Total here is 261,360

7,741,710 + 261,360 = 8,003,070
9 playable stages
8,003,070 * 9 =
grand total of 72,027,630 possible matchups

*Yoshi technically has 6 costumes, but 2 of them (Pink and Dark Blue) are only found in the Yoshi Team (from the 1P Game) and thus cannot be played as by a player.