POKE AA37,00

This removes the command;

DEC (HL)

Which is used to decrease the player 1 life counter held at 96BD.

POKE B1D0,00

This removes the command;

DEC (HL)

Which is used to decrease the player 2 life counter held at 96BD.

Immunity:

POKE AB48,C9

This changes the command;

RET NC

To instead;

RET

Which prevents the rest of the code executing past that point to handle collision detection.

Less Animals:

POKE AEF2,58

See Ending:

POKE 99E1,00

Less Enemies:

POKE 9B16,1E

Always Walk Fast:

POKE AE83,FF

POKE AE85,54

POKE AE8D,BA

AE83	AND A
AE84	RET Z
AE85	DEC A
AE86	LD ($96B0),A
AE89	RET NZ
AE8A	LD (IX+$05),$47

AE83	RST 38
AE84	RET Z
AE85	LD D,H
AE86	LD ($96B0),A
AE89	RET NZ
AE8A	LD (IX+$05),$BA