Getting Multiball Madness in Peggle 2 relies on using Jimmy as your character. Jimmy Lightning is a Winter Gopher and is the second character you unlock in adventure mode.
Jimmy’s ability is multiball, which spawns a second ball when a green peg is hit by the initial ball. It allows the player to hit more pegs with what counts as one ball, thus getting a higher combo and a higher score for the shot.
Mulitball madness is achieved by hitting the final green peg and the final orange peg in the same shot, therefore completing the level whilst multiball is active. Multiball madness gives the player 25,000 points that are added to the score for the level. If you manage to clear out most of the other orange pegs before you use the final multiball, getting multiball madness is not difficult at all.