In-game reset:
Hold L1 + L2 + R1 + R2 and press Start + Select during game play.

Mother Mosquito:
Hold L1 and press Up, Right, Left, Down, Square(2), R1(3) at the character selection screen. A shout will confirm correct code entry.

Father Mosquito:
Enable the "Mother Mosquito" code. Then, hold L2 and press Up, Right, Left, Down, Square(2), R2(3) at the character selection screen. A shout will confirm correct code entry.

Two player mini-game:
Hold Start + Select on controller two after turning on the system. Press Square to move forward, X to jump, and Triangle (when the power meter is full) to do a super attack. Alternately, hold L2 and continuously rotate the Right Analog-stick clockwise at the title screen.