- "Even though you're all new here, I shouldn't have to remind you that this quadrant is key to the Outer Rim."
- ―O'Niner, addressing the troops on the Rishi moon
O'Niner, formally CT-19-7409, was a clone trooper sergeant who served in the Grand Army of the Republic during the Clone Wars. Early in the war, he participated in both the opening battle and the Battle of the Celestial Wake and was later stationed at a listening post in the Rishi system, the only defense against impending Separatist attacks on nearby systems, including Kamino. When the station came under attack by Separatist battle droids, O'Niner ordered for a message to be sent to warn the Republic fleet. The droids, however, disabled the station's beacon, and O'Niner was killed defending the post.
- "Get a message to the fleet! We have to warn—"
- ―O'Niner's last words
The sergeant was born and raised on the Outer Rim planet of Kamino and served in the Grand Army of the Republic during the Clone Wars, assigned to Rishi Station, a listening post on the moon of the planet Rishi. The outpost acted as an outer defense against the Separatist fleet, as well as a lookout post to warn nearby systems of attacking forces. O'Niner commanded the other clone troopers stationed there, most of whom were new and inexperienced troopers whose armor was unscathed and shiny, earning them the mocking nickname, "shinies".
Mid-way into the first year of the war, a group of Confederate BX-series droid commandos, under the orders of General Grievous. attacked the listening post, taking the clones by surprise. O'Niner ordered for a message to be sent to the Republic fleet to warn them of the advancing Separatist forces, but the droids jammed their signal. O'Niner was quickly killed by enemy fire, and the droids took the station, leaving only four troopers—Fives, Echo, Cutup, and Hevy—alive to warn the fleet of the impending Droid attack on Kamino. However, upon the arrival of an clone officer inspection team, Commander Cody and Captain Rex, the clones managed to join forces with them and retake the outpost, eventually disabling the all-clear signal by way of destroying it, which warned the fleet, and the Confederate attack was prevented.
- Rookies (First appearance)