Now you obviously dont have the texture files named correctly according to their slot number bc I dont know why else it could freeze

So take from what the98pika said
This is the list of color slots that you can use:
Pikachu:
00-Original
01-Cap
02-Bandana
03-Googles
Kirby:
00-Original
01-Red
02-Green
03-Blue
04-Yellow
05-White
Sonic:
00-Original
01-Red
02-Green
04-Gold
05-Black
There is no character slot for no.3 for sonic.
For sonic and kirby you can use any of those slots for any textures.
But with pikachu you can only use the character slots that goes with a download for FitPikachu(Number).pcs
So if you see one that says FitPikachu01.pcs you CAN NOT switch it too FitPikachu00,02,03.pcs.
The one thing you need to know is that you have to have the texture names correctly and if the charcater only has lets say 3 or 4 textures you dont add a 5th one. pikachu cant have any texture on any slot, you have to leave texture file of Pikachu Bicenenario alone dont change the number bc thats the required number by default. If this dosent help you then just download the sonic pikachu and kirby texture files from scratch on your own in brawl vault, find a texture you like and your good to go. Remember pikachu isnt a character that you can put a texture in whatever slot you want, you have to follow by the default number of the texture file in the download, no exceptions.

Edit: Please show me all the codes your using, they could be a problem too.