The skull ship looked a lot like the head of the dragon boss at the end of the Gryphon level in episode 2. The eyes looked a bit different, however. I tried to replicate what I did but I had no success. Also, mindless, I tried taking a screenshot but the print screen button only captured a completely black image.
Maybe you just used one of the ships that you can edit with the game's ship editor, I remember it has a skull ship. There are 10 codes in total, and you have to press TAB+*any number key* to change player 1's ship, and CAPS + *any number key* for player 2's
EDIT: where did that duh come from? , ok, it's gone now ;D
Got it too zomg... It happens when i do cheating sometimes. (caps lock + #). It depends on a level you are in. But the scull ship is not good at all. here I have some screens what happened with my ship and settings. P.S.: when I do the cheat, my ship changes in to scull one, and life falls down almost at zero, weapons are changed...