On the Title screen, choose Arcade, then choose 1 on 1 battle. 
On the Character select screen, have Player One choose the Group 
button at the bottom center of the screen and the computer will 
automatically pick the first character on the screen for you to 
play. Have Player One keep winning and keep choosing the Group 
button until all the characters have been chosen and Player One 
has won all the battles. After every Character has been picked 
and won, choose any Character and he will look a bloody skeleton 
(Meat), but will have the Special Moves and Fatalities of the 
Character you chose. 

Note: Meat will not save on the Controller Pak. You will have 
to re-enter the code if you turn the power off to the Nintendo 
64 system.