The Crewmen first appeared in Halo: Combat Evolved in the cutscene with Captain Keyes on the bridge of the Pillar of Autumn and then in actual gameplay when Sam Marcus and Thom Shephard wake John 117 in cryo - two. After John's armor diagnostic a Sangheili major broke in and killed Sam, making a crewman the first person to be seen killed in Halo. Thom was killed by an explosion when he and John-117 attempted to flee. On the way to the bridge several crewmen and Marines are seen skirmishing with Covenant boarders, several others are seen dead. On the bridge, gray uniformed crewmen can be seen pacing about and working at duty stations, this is the last time they are seen in the level. The crewmen are then seen in the next level, Halo, when the player is tasked with rescuing lifeboat survivors.
The only time Crewmen are seen in this game is in the level Crow's Nest. At the base's ops-center a number of grey and red crewmen can be seen operating computers. It's odd that they would be doing this on the ground and not on a naval vessel but this was likely because of the UNSC's situation then - limited resources.
Red: These crewmen wear red uniforms and are the most commonly seen. They seem to be the lowest rank because they are so common. They hold the actual rank of Crewman ranging from recruit to apprentice.
Yellow-orange: Crewmen of this rank wear yellow - orange suits and appear to have the role of technicians, considering Chief tech officer Thom Shephard and his assistant Sam Marcus are of this rank.
Blue: Little is known about this variant. But based on were they appear in Halo: CE they must have some unknown position on the bridge.
Grey: This is obviously the highest rank, because these crewmen are only seen in centers of command such as a ship's bridge. Known members of this rank include lieutenant Dominique and ensign William Lovell.
Crewmen have only engaged in combat in Halo: CE, so they have relatively weak combat AIs. They never take cover from enemy fire and tend to cower when the situation gets too intense, making them more of a hindrance than anything else. Crewmen only fight with magnums and the player never has the ability to swap weapons with them, however this was not implemented until Halo 2.
- The crewmen's uniforms vaguely resemble those used in the TV series Star Trek.
- Sometimes when you find a dead crewman, his pistol will be unusable.
- They are about the equivalent of a modern-day US sailors.
- The technician crewmen are often seen without a weapon.