After the title screen select continue and enter one of the following.

Password	Effect
GCDFGM KKBMNP QRSTVW XDDCDF	Scarecrow joined.
HCDFGS LCCMNP QRSTVW XLMCDF	Yellow clear.
JDGFGX NCCWPP RGSTVW XLMCDF	Tinman joined.
JNPFGJ PCCFPP RGSTVW XLMCDG	Red clear.
KNPNJN PCCFPF RGSBVW ZLMCDG	Cowardly Lion joined.
MNPQRR SCCFPF XGXJVW FLMGDG	Blue clear.
MNPQRT TCCFPF XGBJVC FLMGFG	Wicked Witch defeated.
MNPQRZ TCCFPF XGCJPQ FLMNPG	Purple clear.