Tricia Marie McMillan, usually known as Trillian and sometimes Trillian Astra, is a human astrophysicist and mathematician whom Arthur Dent completely failed to chat up at a party at a flat in Islington. Trillian eventually left the party with Zaphod Beeblebrox, who was directly responsible for her nickname. The next time she and Arthur met was on a spaceship in deep space, six months after their first encounter and shortly after the Earth had been destroyed by the Vogons to make way for a hyperspace bypass.