Wolfchild is one of the infamous definitive games of the 90's.
Press Y, A, B, B, A, Down, A, B, B, A at the title screen. The screen should flash if entered correctly. During gameplay, press Select to end the current level.
Present at 0xF8000. This is the start of the sound driver. All Probe-developed games have a copyright string at the beginning of their sound code.
Music/FX by Probe Software