CT-6666 nicknamed Sixes was a Clone trooper in the Grand Army of the Republic's 501st Legion. Following the formation of the Grand Army of the Republic and the subsequent outbreak of the Clone Wars, Sixes fought against the droid forces of the Confederacy of Independent Systems in a galaxy-wide civil war. At the beginning of the Clone Wars, he was assigned to the 501st Legion and first participated in the Battle of Christophsis under the leadership of Jedi General Anakin Skywalker and Captain Rex.
Sixes, served in the legion in many of the conflicts and battles including Teth, Kamino, Lola Sayu, Umbara and Anaxes in the war and worked and became friends with Appo during the Clone Wars. At the Battle of Christophsis, Despite being a rookie he became good friends with Jedi Padawan Ahsoka Tano. He took part in countless campaigns in the galactic theater of war, from the containment of the Blue Shadow Virus on Naboo and the liberation of Ryloth to other hard-won victories like the Battle of Malastare, the Second Battle of Geonosis, and the Battle of Kamino. He followed and obeyed orders with great efficiency and did not object to General Krell's orders like Dogma and Appo during the Battle of Umbara, when he served under Jedi General Pong Krell in the absence of Jedi General Anakin Skywalker.
At the end of the Clone Wars, Sixes along with the 501st Legion lead by newly appointed Sith Lord Anakin Skywalker lead an attack on the Jedi Temple on Coruscant as part of Order 66 which triggered his inhibitor chip. During the attack, he was promoted to sergeant of the legion following Appo's promotion to commander and was assigned to guard the entrances and exits to the temple, and Sixes was present with Clone Commander Appo on one of the temple's landing pads when Senator Bail Organa arrived to investigate the attack. As Appo was asking Organa to leave, the Jedi padawan Zett Jukassa attacked the clones present, but after wounding Appo was killed by Sixes. Following the end of the war, Sixes retained his rank and continued to serve in the 501st Legion under the command of Sith Lord Darth Vader and Commander Appo.