Wario Land 4 GBA cheats

You can collect special CDs in each level to hear in the sound room.
Here are some of the secret locations where they are found.

Palm Tree Paradise: The CD is hidden in the last cave before the
portal switch. Walk right through the wall from the bottom wooden
platform.
Monsoon Jungle: Smash the block on the floor in the large open
area where enemies throw apples. In the cave, go left and smash
another block, then pound the floor to make the hammer guy jump up
the platform. Get hit to turn into Bouncy Wario and spring up
through the gap to a secret area to find the CD.
Mystic Lake: The CD is at the start, but you 1st need to press
the portal switch. On your way back, smash through the block to
the left of the 1st door.
Wildflower Fields: Float up through the gap at the beginning, then
go left into the clouds. Go up as high as you can, then left. The
CD is at the top.
The Curious Factory (Ruby Passage): Exit right from the portal
switch room. Turn left at Jewel piece at bottom and get flattened.
Go left, then fall into the next screen. Turn right to find the
CD.
The Toxic Landfill (Ruby Passage): Smash through the hidden path
below the 3rd Jewel piece. Smash the 2nd television on the
floor from the top of this path to reveal the CD.
40 Below Fridge (Ruby Passage): After hitting the portal switch,
return to the portal. Once there, go right and up the ladder.
Crawl through the gap and drop down. Smash the block open.
Pinball Zone (Ruby Passage): Just after the 3rd room with black
balls, stand on the slope and press Down to roll right. Now,
climb up to the left to the top.
Crescent Moon Village (Sapphire Passage): Go through the level
until you reach the 3rd outdoor location. Go right and drop down
to the area below. Smash the blocks to far left, then go right to
a slope. Use it to roll left through the wall to a hidden room
where the CD is waiting to be discovered.
Arabian Night (Sapphire Passage): After pressing the portal
switch, you will reach a room with water and flying carpets as you
head back. Fly to top left for the CD.
Fiery Cavern (Sapphire Passage): In the area before you get the
fourth and final jewel piece, you will see a small passage with an
ape that spits ice bubbles at Wario. The CD is to the left through
that passage, but it is difficult getting past the monkey. You
will have to jump over his attacks while crouching.
Hotel Horror (Sapphire Passage): After pressing portal switch, go
to the room 103 which is now unlocked. Use Zombie Wario to fall
through floor to right and grab the CD.
The Big Board: Activate the floors and skip hitting all other
roulettes. When you are in the cave, become flat Wario. Float onto
the red platform. Jump over the gap and you will find the CD.