Unlimited lives:
Locate the two extra lives in the last stage of the Whacky Labs Zone. Collect both of them, then intentionally lose your current life. Repeat this process until you accumulate twelve total lives, then resume game play with unlimited lives.

Zone	Password
1-1	CLQCK
1-2	ZMTHT
1-3	GPPQW
2-1	DJXCT
2-2	WLCSN
2-3	RLHQZ
3-1	JMGVB
3-2	NRWPC
3-3	MDWQL
4-1	MJDSX
4-2	HFLNT
4-3	SPQNG
5-1	DTNZZ
5-2	KQRXH
5-3	JBVMH
6-1	VSNXD
6-2	GRXBS
6-3	WNHJP
Final	STCVC