f25a08f0_Secrets_for_PSP___GameRankings__Unlockable
[How to Unlock] Flame Mammoth [Unlockable] 
In the first room with multiple levels of platforms, get to the very top and jump off to the left onto the edge, you will see an opening in the wall.
Mega Man Maverick Hunter X Cheats, Codes, and Secrets for PSP - GameRankings