Secrets
Mystery Chests
When you are able to control Peach in the castle, there is a room with a treasure chest. Eventually in the game, Peach will put found items in it. To get these items, you have to go to Merluvlee's house. Inside is the chest. Open it and receive the items Peach put inside.
Become NES Mario
In Boo's Mansion, as soon as you enter go straight and a little to the right. Go inside that room. Jump on top of the wooden boxes and then into the vase. Once you come out, you will be Mario from Donkey Kong. To become regular, go back into the vase or exit the room.
Luigi's Diary
After you've beaten Boo's Mansion, go back to your house. Enter your house and keep going straight. You are now in the room with Mario's bed. Notice the floorboards where the diagonal stripes are going the opposite way??? Spin jump and you will be in a secret area. On the desk is Luigi's Diary that you can read.
Toad Town Playroom
At any point in the game, go to Toad Town. Keep going down until you are in the area with the Li'l Oinks. Right as you enter, there is a little strip of land you can walk on. Hit the tree with you hammer and a pipe will shoot out of the ground. Enter through the pipe and you will be in the Toad Town Playroom. (Note* - You need the silver or gold credit from the old Koopa)
Merlee's Spell
In Dry Dry Desert, go to the second area. Then go into the alley to the right of the Toad House. Jump over the wood and you will see a tent with a wizard in it. Merlee can cast a spell on you- good or bad. Most of the good spells come from the most expensive spell. The spells she casts go into effect in random battles.
Original Mario Music
When a new chapter begins, wait a while and you will hear the original Mario music.