You must first enter the Secret Options Menu. When on 
the Character Select screen, choose the Hidden cursor 
with the A Button so your cursor disappears. On the 
Control Pad or Stick, press Up, Up, Left, then press 
Run and Block simultaneously (Default buttons are C 
Left and C Down). When the match starts you will be 
playing as Noob Saibot! 

Note: No Saibot 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.