Zombies Ate My Neighbors and Ghoul Patrol (UP)

Using the Password M15G you can fight this boss right away with the starting weapon, 2 extra lives and a medkit, the starting weapon is pretty weak but can be fired much faster by shooting the boss while up close to it so aim to do that as much as possible, if you die you get a few seconds of invincibility where you can spam attacks right on the bosses too.

For this fight specifically you want to push the boss to the top of the screen and slide left/right under his jumps, turn shoot and repeat, when he turns bright red he will jump faster and send homing fireballs out so instead slide up/down to avoid those and that's the entire fight, you can also see this strategy in the video below.

Ghoul Patrol - Demon Lord Boss - M15G

I tried every password known for Ghoul Patrol. It turns out some passwords got switched. Input the following password M15G to face Demon Lord in this compilation. This is a very tedious, repetitive final boss boss. This also will give you beating Level 18 achievement as well.