Big Lipped Alligator Moment: Tons. It's kind of justified, considering that it was the first full-length Peanuts movie, but it sort of goes overboard on it.
Ear Worm: "Champion Charlie Brown". You'll find yourself humming it a lot, partly because it's sung when Charlie's at his high point. The song even makes a cameo during the opening Cinema Center Films logo.
Actually, the Aesop is "Time heals all wounds (no matter how badly you mess up.)"
Linus: Well, I can understand how you feel. You worked hard, studying for the spelling bee, and I suppose you feel you let everyone down, and you made a fool out of yourself and everything. But did you notice something, Charlie Brown?
Charlie Brown: What's that?
Linus: The world didn't come to an end.
Nightmare Fuel: The Beethoven sequence. Sure, it might be lovely to watch for someone who appreciates the artistic value, but otherwise....