Cheat mode:
Press Left, Up, Left(2), A, B, Y at the game start screen. Change the game type to normal mode and press Start. Choose a character and press Start to display the cheat mode screen. This screen allows stage selection, access to all weapons, and control of the Riddler in the practice mode.

Kill all enemies:
Enable the "Cheat mode" code. Press Start + L + R during game play to kill all normal enemies. Press this sequence multiple times to kill the Boss characters.

Play as The Riddler in training mode:
Enable the "Cheat mode" code. Go to training mode then press Start. Note: You may have to try more then once. Pass The Riddler thug to unlock the Riddler as playable. The Riddler has the following moves:

Moves: Hidden blueprint weapons:

Homing Batarang: Press Quarter-circle Forward + Y.
Bat Cuffs: Press Right, Down + X.
Holographic Decoy: Press Down(2), Forward(2), A.
Rocket Boots: Press Right, Right + X.

Moves: The Riddler:

Repeatedly press X.
Hold Down and quickly and repeatedly press Y.
Hold R and press Back, Down, Forward, Y.
Hold R and press Back, Back, Forward, X.

Moves: Thug 1:

Hold Down, then quickly press Y.
Quickly press Away, Down, Y.
Press Towards, Down, X.
Quickly press Away, Towards, B.
Hold Down and quickly press B.

Moves: Thug 2:

Press Down(5), Y.
Quickly press Away, Towards, B.
Press Down(2), Towards, Y.
Press Towards, Down, Y.
Quickly press Down, Towards, B.
Hold Down then quickly press Y.

Moves: Sug-Spice:

Press Towards(2), X.
Press Towards(2), Y.
Quickly press Towards, Down, Y.
Quickly press Down(2), Away, Y.
Hold Down and quickly press B.

Moves: Ridd Thug:

Press Towards(2), B.
Press Down(5), Y.
Press Towards, Down, X.
Press Down(2), Towards, B.
Hold L and quickly press Y.

Moves: Clown:

Press Towards(2), B.
Quickly press Away, Down, Y.
Press Towards, Down, Y.
Press Towards, Down(2), Y.
Quickly press X.
Quickly press Away, Towards, B.

Moves: Inmate:

Press Towards(2), B.
Press Towards, Down, X.
Press Towards, Down, Y.
Press Towards, Down, B.

Riddler's clues:

"Unlucky ... baker's dozen"
Blast off the elevator's roof and use the grappling hook to reach the 13th floor.

"Steel ... fall through the floor"
Use the grappling hook to yank down the hanging safe and open a secret room in Two-Face's hideout.

"A musical ... rewards"
Knock an opponent into the electric cords on Claw Isle.

"Looking ... found"
Save the hostages by raising your character up with the grappling hook.

Hint: Bonus items:
On level 1 stage 4, after getting the "Credit is given where credit is due" riddle, drop down the hole. Throw a bomb on the left side of the hole. A new hole should appear. Drop down at this location and kick the safes to get a large number of items.

Hint: Hidden coin:
When reaching the electric chairs, go to the door all the way to the right. Do not enter it; when the rope is launched up, a secret door leading to an inmate will appear. Kill the inmate and kick the wall to get a coin.

Hint: Defeating Big Riddler:
To defeat Big Riddler in the final level, you must hit him with contact hits. All other attacks do no damage. Use stick goo then jump kick him. Repeat this until he dies.