O-Four was the nickname of a male Human clone of the Mandalorian bounty hunter Jango Fett. He was created by the Kaminoan cloners on the planet Kamino for use in the Grand Army of the Galactic Republic. Trained as a clone commando, he was made a member of Lambda Squad, serving alongside fellow commandos DD and Sev under sergeant Niner. The squad was deployed to the planet Geonosis during the first battle of the Clone Wars against the Confederacy of Independent Systems. During the fight O-Four, DD and Sev were all killed, leaving Niner as the only member of Lambda. The sergeant later wished he has sent O-Four west with an E-Web heavy repeating blaster during the battle. Like all clone troopers, O-Four was 1.83 meters tall.