Big heads:
While playing a game, press Y, X, A, B(2), A, X, Y.
Funny car:
While playing a game, press Up, A, Down, Y, Left, B, Right, X.
Invisibility:
While playing a game, press Up, Right, Down, Left, click Left Analog-stick, Left, Right, Left.
Low rider:
While playing a game, press Up(2), Down(2), A, B, Y, X.
Low view:
While playing a game, press Up(2), Left(2), R, Black, L, White.
Psychedelic view:
While playing a game, press L, White, R, Black, Left(2), Up(2).
Unknown:
While playing a game, press Y, X, A, B(2), A, X, Y.