Tech Sergeant Chen is portrayed by actor Fred Kwan. Unlike his co-stars, he is friendly with all of them and is a pretty easygoing guy. He was never bitter and regretful of having starred in the Galaxy Quest series, but far more humble than star Jason Nesmith. He generally just follows the others during their public appearances and watches quietly as they bicker amongst each other.
When Jason invites the whole cast to join him onboard the real life NSEA-Protector built by real life aliens, the Thermians, Fred continues to remain easygoing and simple-minded. He showed curiosity and interest in their space adventure and enjoyed the whole experience. In fact, he may have been even more adaptive to his new surroundings than Jason himself. Upon his arrival, he was put in charge of the engine room, much like his fictional position.
In a deleted scene from the Galaxy Quest film, the Thermian engineers ask "Tech Sergeant Chen" various questions on how to solve various technical errors and complications, using all sorts of technical and scientific terms that are obviously beyond human science. Fortunately, Fred tricks the naive engineers into answering their own questions, and "Tech Sergeant Chen" is praised for his genius.
Fred panics just once during their adventure when he was urged to use the digital conveyor to teleport Jason from a planet's surface to the ship. After testing the conveyor on an alien "pig-lizard", and teleporting the creature inside out, which then explodes, Fred was even less confident he could successfully digitize Jason. But he suddenly got his confidence upon the chance to impress the female Thermian, Laliari, and manages to save Jason and successfully teleports him.
During their adventure, Fred falls in love with Laliari. When he shows her how heroic he is with his clever use of the digital conveyor, she begins to kiss him and make out with him. During their make out, she reveals parts of her tentacled true self, but Fred hardly cares, and they continued to make out, much to Guy Fleegman's disturbance.
At the end of their adventure, when the actors return home to Earth, Laliari decides to come and live on Earth with Fred.
Fred returns with the rest of the cast to star in the sequel series, Galaxy Quest: The Journey Continues, with Laliari as a new character and Tech Sergeant Chen's love interest.