Relationships
The movie puts a different spin on the character. The main emotional arc of the movie is a love triangle between Trillian, Zaphod, and Arthur. Trillian is initially attracted to Arthur when she meets him on Earth, but she's disappointed by his apparent lack of spontaneity. During their travels, Trillian discovers that Zaphod may be the more superficially exciting choice, but Arthur is the man who truly cares about her, Arthur commenting when he is about to have his head cut open by the mice that his feelings for Trillian are the only thing that he ever had questions about where the answer made him happy.
In the novels and radio series, Trillian does not have a romantic relationship with Arthur (although when Arthur starts seeing Fenchurch, Ford asks him what happened to Trillian). In the fifth book, Trillian is revealed as the mother of Random Dent. It is unclear for how long (if ever) did Trillian have a relationship with Zaphod. They seem to travel away from each other after the third book, although in the fourth one Arthur states Trillian is with Zaphod, and in the fifth Trillian implies that she hadn't had a child with Zaphod simply because they're of different species. In the sixth novel, And Another Thing..., she pursues a relationship with Wowbagger the Infinitely Prolonged; she accuses Arthur of carrying a torch for her as well.
Read more about this topic: Trillian (character)