Zombies Ate My Neighbors and Ghoul Patrol (UP)

I tried every password known for Ghoul Patrol. It turns out some passwords got switched. Input the following password XVQF to face Samurai Ghost. This guy loves to stay close to you. If you keep moving often this actually throws him off. Trust me the more you'll move the less likely he can attack you. Which also gives you just enough time to do some damage before moving away.

Using the Password XVQF 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.

Not a big strategy for this fight, he has low health so just dodge and get attacks in wherever possible, I found I would get the most damage in during his shuriken attack, if you manage to push up against the boss you can get in a lot of damage and avoid the shurikens altogether, most times I'd find myself running into the boss and taking a hit still but it's a decent trade-off for the damage you'll get in.. Also the boss can't be damaged if he's hanging off the left side of the screen for some reason, so when he gets too far left just run right to reposition him each time.

Ghoul Patrol - Samurai Ghost Boss - XVQF

If you can't defeat Samurai Ghost by jumping to the boss stage (I tried a few times but I couldn't), you can jump to level 6 or level 7 and pick up some better weapons and potions.
Password for level 6 is ST9W and level 7 is 7LBR.

I typed the password for level 6, played through the level, then played through level 7. The boss stage is just after level 7. By the time I reached the Samurai Ghost, I had 0 lives and 0 health kits; however I had a couple of red potions; as soon as the boss fight started I drank a red potion, I spammed the button and the boss died before the potion effect ran out. This method takes a bit longer than skipping straight to the boss stage but it will make the fight much easier.
Bear in mind I had never played levels 6 and 7 (meaning I didn't even know the levels layouts) before and I'm not good at this game, yet I defeated Samurai Ghost on my first try with this method.

Also as soon as I completed the level I reached 250000 score, thus I unlocked the Scorin', scorin', scorin' achievement too