Why is this so hard?

My screenwriting assignment: 3-5 pages. Comedy. Character A wants something from Character B. Character B won't give it.

This is not a difficult assignment. Granted, comedy and short things are both not exactly my forte, but how hard can it be to write two polar-opposite people get into a more-or-less realistic-ish argument over 5 bucks or the cat's bowel movements?

I've now written two scenes that just don't work (one because it's crap, one because it's too far out there and doesn't actually ever descend into chaos and collision so much as a dawning horrible realization), and, I dunno, I guess I just find a fundamentally unstable but benign world boring? I like dead baby jokes or the way Casanova's son's role becomes inverted from comic relief to something absolutely terrible. I like the horror beneath the laughs, not Character A throwing a cell phone at an eagle who's stealing a puppy (yes, really) or the ripped off back of a dress at a party [NOTE: Neither one of these was mine, thank God; hoorah romantic comedies].

That, and I'm very unused to writing screenplays (as I've never done it before), and I've never been good with single scenes, so my whole "Start form this line" or "Start with this scene" or "How best to start up this plot" method of writing has gone splat.

Maybe if I actually map out a few ideas and see if they actually work before writing...?

Meh. @_@