Appo, whose designation as a clone trooper was CC-1119, held the positions of Clone Sergeant and later Clone Commander within the ranks of the 501st Legion during the Clone Wars, serving as a clone trooper officer. Serving the Galactic Republic as a soldier in military service, Appo was a seasoned veteran of numerous significant engagements between the Grand Army of the Republic and the droid armies of the Confederacy of Independent Systems, including the battle of Umbara during the height of the galactic conflict, and on the Republic's capital world, Coruscant, near the war's conclusion. Programmed to offer unwavering loyalty to the Republic, he was a dedicated trooper who followed the directives of his commanding officer without question.
Like all members of the Grand Army, Appo was cloned on the planet Kamino, a world located extragalactic, where Kaminoan scientists utilized the genetic template of Jango Fett, a human bounty hunter, to produce a clone army for the Republic. Prior to his advancement to the military rank of commander, Appo functioned as a sergeant within the 501st Legion, under the leadership of Jedi General Anakin Skywalker and Clone Captain Rex. During the Battle of Umbara, command of the 501st was temporarily reassigned to another Jedi officer, General Pong Krell, because Skywalker had been summoned back to Coruscant by Supreme Chancellor Sheev Palpatine. Sergeant Appo personally observed Krell's readiness to expend his troops, yet he steadfastly carried out the general's commands until Krell's treason was revealed.
In the war's concluding days, Chancellor Palpatine enacted Order 66, declaring the Jedi as enemies of the Republic. Consequently, Appo, serving as the commander of the 501st force stationed on Coruscant, accompanied the Sith Lord Darth Vader as the 501st took part in Operation: Knightfall, invading the Jedi Order's headquarters on Coruscant as part of a systematic purge that spread throughout the galaxy. During the assault, he encountered Senator Bail Organa, employing the threat of force to restrain the Alderaanian politician. However, as Organa attempted to depart, Padawan Zett Jukassa launched an ambush against Appo's unit. He struck down the commander in the lower leg and several troopers until Clone Sergeant CT-0000/1010 "Fox" killed the Padawan.
Appo, also identified by his designation CC-1119, was among the many clone troopers grown from the genetic source of the bounty hunter Jango Fett. He was bred on the extragalactic world of Kamino to serve in a clone soldiers army that had been secretly developed to become the armed forces of the Galactic Republic. Within a years decade of the clone army's commencement, the Republic entered into conflict with the secessionist movement known as the Confederacy of Independent Systems. Consequently, Appo became a soldier in the newly established Grand Army of the Republic, participating in numerous crucial battles across the galaxy during the Clone Wars.

In 20 BBY, by the time of the Republic invasion of Umbara, Appo was serving as a Clone Sergeant within the 501st Legion. Initially, he fought against the Separatist-aligned Umbarans and their military under the command of Jedi General Anakin Skywalker. However, Skywalker was summoned back to the Republic capital of Coruscant, which left Appo and the legion under the command of a different officer, the Besalisk Jedi General Pong Krell, throughout the duration of the campaign.
Following a failed attempt to invade the Umbaran capital city, Krell and the 501st were assigned to secure a heavily fortified Umbaran airbase that was essential to the Republic's strategy. Under the General's direction, Clone Captain CT-7567 "Rex" spearheaded an initial assault on the base's defensive perimeter, while Appo and the majority of the 501st remained with Krell, who observed the battle from a clifftop in the distance. Krell then instructed Appo to organize the remaining troops into platoons, consisting of clone troopers and AT-RT drivers. As Rex and his men sustained casualties while fighting Umbaran mobile heavy cannons, Appo informed Krell that he had completed the task of forming the platoons. The sergeant also expressed his desire to immediately dispatch the troops to assist Rex on the battlefield, but Krell dismissed Appo, stating that he would issue the order when necessary. When Rex contacted Krell via hologram, Appo held the device in his hand. The Besalisk then spoke to the captain, who had devised a plan to infiltrate the airbase using Advanced Recon Commando CT-5555 "Fives" and the trooper, "Hardcase." Krell did not endorse the plan, but Rex proceeded with it regardless.
From the clifftop, both Appo and Krell witnessed the return of Fives and Hardcase aboard two commandeered Zenuas 33 Umbaran starfighters, which resulted in the destruction of the mobile cannons. Upon noticing that the airbase's defensive systems were disabled, Krell ordered Appo to mobilize the spare platoons and attack the airbase. Appo's men successfully seized the airbase, forcing the remaining Umbaran troops stationed there to surrender. With the airbase captured, Krell and the rest of the 501st Legion fortified their position within the base.

After learning about the destruction of the Confederate supply ship in orbit above Umbara, Krell instructed Appo to bring the surviving perpetrators, Fives and Jesse, to him in the airbase's central command tower. Appo relayed the order to Fives and Jesse, and the clones met with Krell in the tower. Krell informed the two clones that, due to their disobedience of a direct order, they would be imprisoned for their actions and sent to the Grand Army's court-martial.
Despite the initial plan to court-martial them, Krell used his authority to sentence them both to execution by firing squad because a court-martial would take too long. Rex, accompanied by Appo, was instructed to escort Fives and Jesse to the location of their execution. As Appo stood beside the handcuffed Fives and Jesse, the firing squad prepared to shoot the two clones, but their focus was disrupted when Fives pleaded with them to reconsider. Dogma, however, disregarded Fives' words and commanded the firing squad to open fire on the two clones. Fives' words did have an impact, however, which caused them to misfire. Rex ordered Appo and another clone to remove Fives and Jesse's binders. However, on Krell's orders, the two clones were taken back to the airbase's prison, while Rex's men mobilized to attack Umbaran soldiers that had disguised themselves as clones.

Subsequently, it was discovered from a dying Clone Lieutenant Waxer that Krell had issued the same order to his platoon from the 212th Attack Battalion to hunt down disguised Umbaran soldiers, deliberately knowing that the "enemy" would be actual clones. In response to the fallen Jedi's actions, Appo joined Rex and the clone troopers who went to the airbase's central tower to arrest Krell for treason against the Republic. Despite surrounding the Besalisk Jedi, Appo and the other clones were quickly repelled by Krell with the Force before the fallen Jedi used his two duel bladed lightsabers to break through the window of the central tower and disappear into the nearby jungles. Pursuing Krell, Appo and the rest of the clones were briefly halted in their pursuit by Dogma, who was still loyal to Krell, however Rex was able to quickly talk Dogma down, with the defiant clone being apprehended. Appo then followed close behind Rex and Fives as they maneuvered through the Umbaran jungles with the rest of the clones before being suddenly ambushed by Krell. Despite sustaining a number of casualties, they successfully apprehended the former Jedi. Krell then explained that he was a Separatist sympathizer, wanting to become Count Dooku's apprentice. Krell was ultimately executed by Dogma, who was the former Jedi's most loyal follower until Krell admitted his betrayal. With Krell dead, Appo and the rest of the 501st troopers regrouped outside the prison. The Republic had won the battle.
In 19 BBY, during the Clone Wars' final days, the Republic faced a simultaneous Separatist assault on Coruscant and a crisis on Mandalore. General Skywalker decided to split the 501st to address both threats, promoting Captain Rex to Clone Commander of a new division, the 332nd Division. Appo remained with the original 501st force, returning with that part of the legion to Coruscant. Despite keeping his sergeant rank, Appo was made the commanding officer of that 501st half during the return to the capital.

Shortly after the Republic's victory on Coruscant, Darth Sidious—the Dark Lord of the Sith who orchestrated the fall of democracy disguised as Supreme Chancellor Sheev Palpatine—activated Order 66, a secret protocol implanted via a behavioral modification biochip that compelled every clone in the Grand Army to eliminate the Jedi leadership. With Rex away, executing the order aboard the Tribunal, Appo, as the highest-ranking officer on Coruscant, oversaw the 501st troopers' execution of Order 66 and was promoted to Clone Commander. Led by the newly appointed Sith Lord Darth Vader—formerly the Jedi Knight Anakin Skywalker—Appo and the 501st participated in Operation: Knightfall and attacked the Jedi Grand Temple. The clones proceeded to slaughter their former allies, including Padawans and younglings. Appo and his men coordinated effectively against the Jedi, aided by the element of surprise. Within hours, the Temple was secured and the fighting ended.

The Jedi headquarters attack created a fire visible in Coruscant's Federal District night sky, drawing Alderaanian Senator Bail Prestor Organa to the Jedi temple. Appo, with a clone contingent, prevented the senator from entering. Echoing the idea enforced by his control chip, he claimed the Jedi had started a "rebellion" that the 501st was suppressing. When Organa ignored the block, Appo threatened the politician with a blaster. However, their encounter with Organa distracted the clones from the approaching surviving Padawan Zett Jukassa, who killed and wounded several soldiers, including Appo, who was struck in the lower leg by the apprentice's lightsaber. Jukassa was killed by Clone Sergeant Fox, and Organa escaped in horror, with the sergeant ordering his men to let the Senator go.

Appo was a human male clone of Jango Fett. Therefore, Appo had the same physical characteristics as his clone template, standing at 1.83 meters tall with black hair, brown eyes, and tan skin.
For most of his life, Appo had been trained to be a soldier of the Galactic Republic. He was skilled at armed and unarmed combat, military tactics, reconnaissance, and peacekeeping. Like his clone brothers, he was also conditioned to be completely loyal to the chain of command, obeying every order without question. Although he saw Pong Krell's willingness to sacrifice clone lives for victory, Appo was still loyal to his general until the Besalisk Jedi was discovered to have betrayed the Republic.
Appo's loyalty was reinforced through programming in the form of a behavioral modification biochip, which ultimately ensured Darth Sidious' control over clones like Appo. Appo followed the command to execute Order 66, participating in the attack on the Jedi Temple with Anakin Skywalker and the 501st Legion. Like other clones influenced by the biochip during Order 66, Appo believed he was suppressing a "Jedi rebellion" against the Republic. When Bail Organa confronted him at the Jedi Temple, Appo tried to reassure him that the 501st was in control. However, when Organa tried to enter the Temple, Appo raised his weapon and ordered the senator to leave.

As a clone soldier serving the Republic, Appo was equipped with Phase II clone trooper armor, which replaced the original Phase I version as the standard armor for Grand Army clone troopers. His armor had the 501st Legion's common blue markings. As a sergeant, Appo's helmet had a white arrow shape running down its forehead. However, the symbol was absent from Appo's armor during the Jedi Temple siege. In combat, he used the DC-15A blaster carbine, DC-15A blaster rifle, and two DC-17 repeater hand blasters. His utility belt also had a N-20 Baradium-core thermal detonator.
When Appo was a Clone Commander, his armor had a black and blue left-shoulder pauldron, two black bandoliers with three white pouches each—one over the right shoulder to his pauldron and the other around the upper right arm, a black kama, and dual holsters for DC-17 hand blasters. He also used a BARC speeder during that time. The armor customizations were not worn during Operation: Knightfall.
CC-1119 first appeared in Star Wars: Episode III Revenge of the Sith in both the current canon and Legends continuities. George Lucas directed the film, released in 2005. Temuera Morrison voiced CC-1119, and like all other clone troopers in the film, was portrayed entirely with computer-generated imagery. The Star Wars: The Clone Wars fourth season episode "The General," directed by Walter Murch and released in 2011, first identified the trooper as "Appo." Appo's designation "CC-1119" was first identified in his Star Wars: Force Collection character card, released in 2014 by Konami.
Dee Bradley Baker voiced Appo in the Star Wars: The Clone Wars television series, as he did for all clone troopers in the show. The arrow on Appo's helmet is a nod to Baker voicing Appa, a character from Avatar: The Last Airbender, a show that The Clone Wars supervising director Dave Filoni had previously worked on.
Although Star Wars Helmet Collection 16 says that CC-1119 was promoted to commander when Rex abandoned his post and Order 66 was issued, Star Wars: The Clone Wars: Character Encyclopedia - Join the Battle! says that CC-1119 was promoted to commander after the Battle of Umbara and commanded the 501st unit that went to Coruscant while Rex led the 332nd Division. Because The Clone Wars: Character Encyclopedia is the newer source, this article assumes that information is correct.