You must beat the game once. At that point you can purchase him from the move shop for 1 million smash points.
go to one of the car dealerships (the building with the giant monkey on top) pick up the monkey jump up and you'll fall slowly.
Complete the game once on easy or normal mode to unlock hard mode, play again mode, abomination character and the ability to purchase savage banner.
Enter the following in the cheats(passcode) menu:
FROGGIE - Wild traffic.
CHZGUN - Cow missiles.
SMASH# or SMASH## - Replace # with 5, 10, or 15 for that multiple of Smash Points