Gag Halfrunt is the private brain care specialist of Zaphod Beeblebrox and Prostetnic Vogon Jeltz. Halfrunt describes Beeblebrox as "Just this guy, you know?" In the radio series and books, he is responsible for the order to destroy Earth. His reason is that if the ultimate question is revealed, everybody would be happy and psychiatrists would be put out of business.
In The Restaurant at the End of the Universe, when he learns of two escaped Earth people (Arthur and Trillian), he orders the Vogons to attack the Heart of Gold, at around the same time when Arthur unwittingly sabotages the ship's computers upon asking for a cup of tea.
Halfrunt was played by Gil Morris in the TV show and by Jason Schwartzman in the movie. In both these versions he only appears briefly.
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