After you've beaten the game, a single UFO will appear in each stage in chronological order. If you destroy ten of the UFOs and their alien pilots as they try to escape, Jody will briefly sing for you. If you destroy all 14 of them, Jody will say a special message and congratulate you as the President of Outer Space.

Unlockable	How to unlock
Jody's "Ten Little Aliens" Song	Destroy 10 UFOs and their pilots.
Jody's Special Message	Destroy all the UFOs and their pilots.
UFO Missions	Beat the game.