OH!!! I get it now! It took me a little bit but I get it now! It's like another story I read called The Ghost Next Door. I had to read it twice before getting it. *hits self*

Oh well, thanks for the knowledge!^^

*does first comment dance* This story made me shiver! I don't know why depressing stories draw me in. I'm the "yay for happy endings kinda' girl". I also don't know why I love making sad stories myself. Like all your stories, this was amazing...but I do have to admit that I didn't understand the ending. "It was Gaz." I think I may have missed something...I dunno'. All in all, it was magnificient.

Um...I shall try and clarify.
Zim basically tells Dib that all humans die and that there's nothing he can do but move on. Dib says 'it's different'...(as in the situation he's in doesn't allow him to do that). Zim asks Dib 'Why it's different' and Dib tells him 'because...it was Gaz'( As in, it was Gaz who had died, not just some human). This signifies how much Gaz meant to him, and lets the readers know that she is indeed dead.
I'm sorry it was confusing. This comment is probably confusing too. Eh. Thanks for reading!!