Low G Man is a pretty tough game, and once you finish it (if you make it that far) you still haven't fully completed it. You have to go through the game 3 times total to see all of the endings.

Unless you put in some passwords to help out.

Put in this password to see the first ending:

This one to see the second ending

And this one to see the third (and final) ending

All of the endings are essentially the same

Just with a couple of screens changed at the end, so you might want to just skip the first and second and go for the third ending.

Or not, your call.