Why is it "Do a Barrel Roll" and not "Does a Barrel Roll"? [closed]

Does a barrel roll?

is a question asking whether a barrel rolls.

Do a barrel roll!

is an instruction ordering the pilot to perform a barrel roll.

This comes from the video game Star Fox 64.

In it, you fly around in a ship shooting stuff, and getting shot at by stuff. If you "do a barrel roll" (rotate your ship quickly along its axis of flight ie. rotate its roll), you are momentarily invincible.

Because of this, one of the other characters constantly contacts you over the radio to tell you to "DO A BARREL ROLL!" It became increasingly annoying and inappropriate, because by the end of the game I know when to do a friggin' barrel roll already!

Because it was repeated so often, the phrase became engrained in our minds. And because the game was so popular, the phrase soon became an Internet meme

"Barrel roll" is a noun (it's a maneuver that airplanes can do). "Do a barrel roll" is an imperative phrase where "barrel roll" is the direct object.

I take the verb to be an imperative, so Do a Barrel Roll seems fine.