Just me making random associations,

Has anyone else realized that they ONLY know Toothless is the night fury because of his sounds?

Nobody had actually ever SEEN a night fury. They didn't know what they looked like until Toothless. So when he appears at the arena to defend Hiccup, they immediately know it's the night fury BECAUSE of his plasma blast and whistling wings.

Hiccup knows Toothless is the night fury because he shot down the dragon, the invisible dark beast with the plasma and speed.

But his fellow villagers didn't know Toothless existed. Meaning when he shows up, they only know the night fury off noise, not appearance. Hence the famous "night fury, get down" line when they hear him, not even see him.

So without meeting Toothless, they would NEVER know a night fury based off LOOKS. They'd have no idea what it actually looks like. Just what it sounds like.

Sorry if this is a lame point! I just found it cool.