Kixx is shown to be a talented kickboxer and loves to pick fights, which would consider him a bully. He also appears to be exceedingly dim-witted, but slightly hotheaded. However, after Lilo and Stitch befriended him, Kixx has shown to control his temper a lot better.
Although not the brightest, Kixx is loyal to those who win his trust. He is valiant and an excellent fighter, but also a really big softie deep down. He enjoys kickboxing, wrestling, and baseball and shows a sign of pride. He is also very slow-witted and foolish, as well as ill-tempered, extremely aggressive, and excessively violent.
Experiment 601 was the 601st experiment to be created by Jumba with Hämsterviel's funding. He was designed to use his kickboxing skills to beat up and defeat enemies. 601 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.
All of the experiment pods were released and scattered across the island of Kauai, with 601's pod landing by a cliff face.
When a dehydrated tourist threw a half-full water bottle over the cliff, it landed near a ravine and trickled out water, which touched 601's pod, activating the experiment. 601 then attacked a couple, beating them up when the husband angered him.
Later, 601 proceeded to attack and beat up additional tourists who stood in his path.
When Lilo and Stitch arrived to find and capture 601, the latter ambushed them. Stitch prepared to fight 601, but ended up faltering due to an earlier snack combo incident in which Stitch's combat training was erased. Lilo was then forced to retreat with Stitch, while 601 was distracted with beating up the newly-arrived Gantu.
While 601 continued his rampage, Jumba lent Lilo several books, including one titled Fighting Four-Armed Monsters, to help her re-train and condition Stitch to fight in combat. After he mastered a few training exercises, Stitch was practically ready to battle 601 hand-to-hand.
601 later attacked a beach gym, where he defeated all the boxers with ease. Stitch then came to challenge 601 to a rematch and had a prolonged battle. At first, 601 was able to easily overpower Stitch, but with Lilo's tutelage and Stitch's coordination, the latter easily defeated 601, who was restrained with ropes.
601, christened Kixx, was shortly after found a one true place teaching other people kickboxing. Back at Gantu's ship, Experiment 625 and an injured Gantu watched a TV commercial of Kixx hosting his own instructional workout video. It motivated Gantu to learn kickboxing after being pummeled by Kixx.
Kixx reappeared in "Elastico" as one of the audience members for Lilo's hula dance.
In "The Asteroid", Kixx was one of the six experiments that Stitch convinced to come with him and Lilo to save Earth from an approaching asteroid. Along the journey, Kixx kicked the back of Spooky's seat, causing the latter to terrify him. Also, when Kixx grabbed at the free refreshments, only to get slapped by Pleakley, the former beat Pleakley up and took a bag of peanuts for himself. He later endured a clobbering from Hammerface and helped Stitch remove the ship's hyperdrive engine.
Kixx made a brief cameo in "Houdini", hosting his recent kickboxing commercial.
In "Angel", Kixx was one of the experiments that Angel reverted to evil using her song, causing the former to beat up athletes, and thus forcing Stitch to fight and defeat him again. Later, Kixx and the other depraved experiments attacked Stitch aboard a ship, but Angel turned them back to good before Kixx could land the fatal blow. Working together, the experiments were then able to successfully escape the ship with Stitch.
Kixx reappeared in "Slugger" as part of Lilo's softball team.
Kixx was one of the experiments in "Checkers" that joined Stitch in a rebellion against Gantu. Although he did not appear during the battle, he was seen rebuilding the float after Gantu's defeat.
In "Ploot", Kixx was one of the first team of experiments (along with Deforestator and Richter) formed to try and stop Ploot. However, Ploot was easily able to defeat them, forcing the three experiments to retreat.
The first 624 experiments, including Kixx, were rounded up by Leroy and taken to a stadium to be destroyed. However, Lilo, Stitch, Jumba, Pleakley, Reuben and Gantu arrived before the experiments could be destroyed.
Kixx participated in the following battle between the experiments and the Leroy clones by beating up attacking Leroys.
However, the Leroys soon gained the upper hand in the battle, but were defeated when Lilo, Stitch, Reuben and several other experiments performed the song "Aloha ʻOe", which caused the Leroy army to shut down due to the original Leroy's fail-safe. Kixx joins them for the song by playing the bongos.
Kixx made an appearance in the Stitch! anime along with Pix, Boomer, Slushy, Blowhard, and Slugger when Yuna and Stitch visited Tokyo Disneyland. He makes a second appearance where Hämsterviel modifies him with a new samurai style of fighting, along with a samurai outfit to match it.
- Kixx was first revealed in a DVD bonus feature of Stitch! The Movie in the experiment gallery.
- Kixx is named after the soccer team, Philadelphia KiXX.
- Kixx's appearance and mannerisms greatly resemble the Tasmanian Devil from Looney Tunes.
- Kixx was also mistaken for a wild, four-armed purple pig by two tourists and a radio announcer.
- The climactic battle between Kixx and Stitch is presented in a western-style theme.
- Kixx's holographic silhouette appeared in both "Amnesio" and "Fibber".
- Kixx's pod color is blue.
- Kixx is described by the experiment computer screen as "Experiment 601. Primary function: Hand-to-hand combat."
- Kixx bears some resemblance to Machamp from Pokémon, even being muscular, having four arms, and highly skilled in physical combat.