NARRATOR: Repulsed by her haggard appearance, the prince sneered at the gift and turned the old woman away. But she warned him not to be deceived by appearances, for beauty is found within.
Once again, we're setting up the ground rules early so that everyone knows what's going on. What you see isn't always what you get.
MERCHANT: But behind that fair façade /
I'm afraid she's rather odd.
The villagers literally don't see past anyone's appearance, not only missing Belle's kindness and generosity of spirit but actively pooh-poohing anything about her that they don't get. Like reading, for instance.
GASTON: Here in town there's only she /
Who is beautiful as me /
So I'm making plans to woo and marry Belle.
Gaston falls into the same trap as the villagers, but he goes even further: disregarding her inner self entirely and viewing her quite literally as a trophy wife.
LEFOU: No one's slick as Gaston /
No one's quick as Gaston /
No one's neck's as incredibly thick as Gaston!
We won't repeat the whole song (though have a listen; it's a good one), but pay attention to the lyrics. Everyone is praising Gaston's body and the various things he can do with it. (G-rated things…come on, people, get your minds out of the gutter.) But, not one of them talks about who he is inside. They don't care about that kind of stuff.
BEAST: She's so beautiful and…well, look at me!
The Beast knows he's monstrous-looking and assumes that Belle will see him just as others do.
BEAST: She'll never see me as anything but a monster…it's hopeless.
This is the Beast's lowest moment: his absolute despair at ever being restored to being human. But, at least here he acknowledges that his inner self is what's important, not his outer self.
GASTON: Everyone knows her father's a lunatic. He was in here tonight, raving about a beast in a castle.
MONSIEUR D'ARQUE: Maurice is harmless.
GASTON: The point is, Belle would do anything to keep him from being locked up.
This is a disturbing moment, and not just because the villain is busy "persecuting harmless crackpots." He clearly knows that Maurice isn't dangerous but willfully chooses to focus on appearances. If Maurice acts crazy, then he must be crazy, and the obvious evidence to the contrary doesn't matter a bit. As we have noted, Gaston's kind of a jerk.
GASTON: It's a beast
He's got fangs
Massive paws Killer claws for the feast!
Notice how Gaston stresses the Beast's animal-like appearance here, making him a natural target for "the greatest hunter in the whole world." His mistake? The Beast is more than he appears—in this case, he's more than just another animal.
GASTON: What's the matter, Beast? Too kind and gentle to fight back?
This is Gaston's blackest moment of villainy. He sees past the appearance to the Beast's soul, he knows what the Beast truly is, and he views it as a weakness instead of a strength. Straight off the nearest cliff for you, Gaston!
GASTON: Put me down. Put me down. Please, don't hurt me! I'll do anything! Anything!
Here's a shocker: like most bullies, big bad Gaston turns out to be quite the gutless wonder. We're curious if anyone would've sung songs about him down in the tavern if they'd seen that coming.