00 = Mario
01 = Donkey Kong
02 = Link
03 = Samus
04 = Zero Suit Samus
05 = Yoshi
06 = Kirby
07 = Fox
08 = Pikachu
09 = Luigi
10 = Captain Falcon
11 = Ness
12 = Bowser / Giga Bowser
13 = Peach
14 = Zelda
15 = Sheik
16 = Ice Climbers
17 = Marth
18 = Mr. Game & Watch
19 = Falco
20 = Ganondorf
21 = Wario / Wario-Man
22 = Meta Knight
23 = Pit
24 = Olimar
25 = Lucas
26 = Diddy Kong
27 = Pokemon Trainer
28 = Charizard
29 = Squirtle
30 = Ivysaur
31 = Dedede
32 = Lucario
33 = Ike
34 = R.O.B.
35 = Jigglypuff
36 = Toon Link
37 = Wolf
38 = Snake
39 = Sonic
40 = Mewtwo
41 = Roy
42 = Knuckles

The last true costume values should be no later than 0x62-0x63!

WARNING!! Do not place any Wario costume ID at 0xF (15), 0x1F (31), 0x2F (47) or 0x3F (63). These break the game if you try to load Wario-Man
from the CSS. There are enough IDs to still give him 50, so simply select a different value instead of using those specific four.
Mr. Game & Watch has two known unusable costume slots: 0xB (12) and 0xC (13). These are designated by red colors inside his costume .pac file.