Star or Planet?

Transcript
(David and Callie are looking at the night sky)

Callie: Is that a star or a planet?

David: What makes you think it has to be one of those two things? There are a whole bunch of things it could be. It could be a comet, an asteroid, a satellite in geostationary orbit, a glow-in-the-dark weather balloon, a non-moving planet, an extra-large high-altitude firefly, or...

(Callie leaves)

Callie: Forget I asked.

David: It's probably just a star, though.