At the Galaga Arrangement title screen, press Left, Right, Left, Right, Up, Down, Up, Down.
In Galaga, when you see the ship with a purplish beam, fly into the beam [make sure you have at least two lives].
The beam takes your ship. Shoot the ship that took your ship, then your ship comes back with your other ship and you have a double ship.
In Toy Pop, if you die, keep pressing Select, then X