Beat the game in 125, 250 & 500. Go to Options, then Extras and go down to watch the video.
All classes
Enter "ALL_EVENTS" as a name at the name entry screen in championship mode or after finishing a race. Note: "_" indicates a space.
All tracks
Enter "DIRT_TRACKS" as a name at the name entry screen in championship mode or after finishing a race. Note: "_" indicates a space.
Big head mode
Enter "GROSSE_TETE" as a name at the name entry screen in championship mode or after finishing a race. Note: "_" indicates a space.
Mirror mode
Enter "OPPOSITE_LOCK" as a name at the name entry screen in championship mode or after finishing a race. Note: "_" indicates a space. Alternatively, successfully complete the open class championship. Then, choose the "Race Settings" selection under "Options" to access the "Mirror Mode" selection.