Hehe... You could probably be describing about half of Coulton's discography.
A couple possibilities, however:
-Chiron Beta Prime - A family trapped on a slave planet by their robot overlords (did I say overlords? I meant protectors...) frames their plea for help as a Christmas letter.
-Re: Your Brains - The last survivor of a zombie apocalypse gets a "corporate pitch" from his annoying coworker (now a zombie) about why he should let them all in so that they can eat his brains.
-Skullcrusher Mountain - a mad scientist sings a love song to his abductee in mad-scientist logic.
I don't think these are what you're looking for, but other Coulton songs you absolutely should check out:
-The Future Soon
-I'm Your Moon
-You Ruined Everything
-When You Go
-I Crush Everything
Hope this helps.
-Adam