Practice mode:
Enter 9005 as a password to practice in any stage and level except for the Bosses and Master.

Level	Password
Jammin' Jungle
Stage 1	(none)
Stage 2	6800
Stage 3	5120
Boss	7420
Vexin' Volcano
Stage 1	4501
Stage 2	8111
Stage 3	7421
Stage 4	1051
Boss	3351
Slammin' Sea
Stage 1	4502
Stage 2	8112
Stage 3	7422
Stage 4	1052
Boss	3352
Crankin' Castle
Stage 1	0513
Stage 2	8114
Stage 3	9723
Stage 4	3353
Boss	5653
Thrashin' Tundra
Stage 1	2814
Stage 2	8115
Stage 3	1134
Stage 4	5654
Boss	7954
Cruisin' Comet
Final stage	0515

Hint: Set off all bombs:
During battle mode, walk in one direction and quickly press C(2) to set all of your bombs at once in a row.