Brett was played by the late Harry Dean Stanton in Alien.
He was the engineering technician aboard the commercial towing vehicle USCSS Nostromo and worked closely with Parker for that purpose.
He was serving on the ship during its fateful voyage in 2122 when it encountered a Xenomorph on LV-426, an incident arranged by Weyland Yutani corporation. It eventually led to the decimation of its crew by the Xenomorph, the destruction of the ship in an attempt to stop it and the loss of all but one of its crew, Ellen Ripley, who defeated it.
He, together with Parker, dealt with the repairs of the ship, when it landed on the moon. He witnessed the "birth" of the Alien, when it came out of Kane killing him.
Brett was the first victim of the fully-grown Alien, while they were searching it believing it to be still small after coming out from Kane. During the search he received the order to find Ripley´s cat so that it won´t disturb the mission and was killed by the Alien from the rear during his attempt to catch it.
Director´s cut Edit
There Brett is shown to have been turned into an egg. This egg was destroyed by Ripley with the help of her flamethrower together with Dallas, whose fate was going to be the same.