Dance Dance Revolution - Konamix cheats and cheat codes for Playstation

Under Yuni's skirt
Choose "Yuni" from secret collection. 
During the game, you can see up her skirt.

Emi without a hat
At the selection screen highlight game mode, solo mode or workout mode. 
Then, hold Right and push X.

Link mode
Choose game or solo mode, then press Left, Left or Right, Right.

Secret songs
Choose solo or game mode. Play 3 songs to unlock a secret song. 
Next, play different songs in a different order, then play the hidden 
song as the 3rd song. If does not work for the first time, try again.
The hidden songs will be marked as "NEW!" and will be highlighted in green.

Be sure, all of your songs have a Grade B or higher.
When you get all the songs you will have 20 secret songs. 
Here are the list of secret songs:

Trip Machine (Luv Mix)
Superstar
R3
Paranoia Rebirth
Orion . 78 (AMeuro-MIX)
Matsuri JAPAN
Let the Beat Hit Em' (Classic R&B Style)
Leading Cyber
La Senorita Virtual
Holic
Healing Vision 
Genom Screams
Era (Nostal Mix) 
DXY!
Drop Out
Do It Right
Dive
Can't Stop Fallin' in Love
AM-3P 303 Bass Mix tkz remixed by U1
Absolute