Tetris DS Unlockable

Unlockable How to Unlock
Basement Tetris (SMB 1-2) Get to Level 3
Mario Tetris 3 (SMB 3 Overworld) Get to Level 4
Bowser Battle (SMB 1-4) Get to Level 10
Tetris DK (Push Mode Theme) Get to Level 13
Balloon Tetris (Touch Mode Theme) Get to Level 14
Tetris Climber (Ice Climber Theme) Get to Level 15
Rushed Tetris Get to Level 16
Ancient Tetris (Tetris GB - Music A) Get to Level 20
CongraTetris Finish Marathon (Get over 200 lines)

Endless Mode in Standard Mode
To unlock this, you have to finish Standard Mode. (Get over 200 lines) This will be accessible as a switch when picking the Level in Standard Marathon Mode.