On Lungens And Dragons, hit anything that can be destroyed. When it says "Map destroyed", look for the sword in the rock to find the secret weapon. The same can be done on all levels for different weapons. Note: If you use Jerry, Nibbles. or Tom, you may get a costume on Lungens And Dragons. On the western level, you can unlock a costume with Tom, Nibbles, and Spike.
Unlimited lives
Press Right, Right, Up, Left, Up, Right, Down , B , A , Select, Start and Start again at the title Screen.