Secret Song Rock Style (a remix of Infinity Blue) - To unlock this song, use LIGHT as your character, play challenge mode, and choose Infinity Blue to play on whatever level you like. It will automatically change to Rock Style. Just pass it and it will stay in the song selection list from your next game onwards.

Unlock the hidden items temporarily - At the title screen(which tells you to PRESS START BUTTON), enter the following code. You can unlock the coorsponding items for the current session.

These Item will NOT be saved when you save the game, and you need to enter these codes again once you have accessed the Gameover screen if you want to keep their effect.
The numbers correspond to the Pop'n controller's buttons from left to right.

Code - Effect

37373748 - Unlocks AC pop'n music 13 hidden songs and their characters
31168631 - Unlocks CS pop'n music 13 hidden songs and their characters
48973642 - Unlocks ee'MALL hidden songs and their characters
19837643 - Unlocks hidden EXPERT Courses and the EX chats

Unlock the song Samba de Classic - To unlock the song in mini game mode, simply clear all 3 events without fail in Harmanov Cup mode. You'll be rewarded with Samba de Classic

Samba de Classic - Clear all events in Harmanov Cup mode.