An experiment of few words, Yang was shown to be fiery, short-tempered and hotheaded before his rehabilitation. He is single-minded and will focus only on what is right in front of him, paying little heed to anything else going on around him. This clearly demonstrates overconfidence in his own powers, as Yang considers them more than adequate to handle any threat. He is shown to not really care what other people want him to do, and has a tendency to be boastful. However, he would defend his friends and ʻohana loyally, alongside Yin.
Yang is a quadrupedal, orange-and-red weasel/lizard/dragon-like experiment with volcano-like spouts along his back, two volcano-like antennae on his head, black eyes, a round nose and a wide mouth with two fangs sticking out.
Yang can fire balls of lava from the spouts on his back at targets and enemies, and heat solid ground or other land with his feet. It is also shown that when Yin and Yang combine their powers, they are able to create rock/land.
Experiment 502 was the 502nd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to spout balls of lava. 502 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 502's pod landing in a fissure in the ground on a mountain road.
When a stranded man poured water into his jeep's burnt-out engine, the water leaked out into the fissure and onto 502's pod, activating the experiment. 502 then erupted to the surface and set out to cause chaos.
While 502 was attempting to cross a road in front of an approaching car, the owner scolded him to get out of the way, causing the angered experiment to destroy the driver's automobile.
502 later entered Kokaua Town and went on a rampage, destroying everything in sight. Stitch jumped onto one of 502's back spouts to try and stop the latter, but 502 simply blasted Stitch off and most likely continued his rampage.
Stitch's incompetence caused a rift between him and Lilo, and the two insisted that they each could catch an experiment without the other. After wagering an official contest, Stitch joined up with Jumba while Lilo joined up with Pleakley.
502 was later chased by Stitch and Jumba through a jungle, but the two failed to catch the former. While continuing to flee his pursuers, Experiments 502 and 501 met for the first time. Jumba erroneously stated that if they both touched, Earth would likely be destroyed. However, they were ambushed and captured in containment orbs by Gantu before they could make physical contact.
When Lilo later tracked 502 down, the latter attacked her with fireballs. However, Lilo was able to block off 502's lava attacks long enough for Stitch to immobilize 502 via anti-heat foam, rendering him defenseless.
501 and 502 were then rehabilitated, named Yin and Yang, and given a one true place using their combined powers to create a whole new island.
Yang reappeared in "Elastico" as one of the audience members for Lilo's hula dance.
In "Houdini", Yang was one of the audience members for Stitch's bungled magic act.
In "Dupe", Yang was one of the experiments that came to Lilo and Stitch's slumber party wearing boxer shorts and bunny slippers. However, he was forced by Pleakley to leave due to his destructive behavior.
In "Angel", Yang was one of the experiments that Angel reverted to evil using her song. Later, Yang and the other depraved experiments attacked Stitch aboard a ship, but Angel turned them back to good before they could finish Stitch off. Working together, the experiments were then able to successfully escape the ship with Stitch.
Yang reappeared in "Slugger" as part of Lilo's softball team.
In the film's opening, Yang can be seen waving hello to Lilo, along with Yin and Cannonball. He was also seen later in the movie creating a new island with Yin as Lilo was making her rounds with Scrump to make sure all the experiments were happy in the one true place they belonged.
Later, the first 624 experiments, including Yang, 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.
Yin and Yang participated in the following battle between the experiments and the Leroy clones by using their combined powers to encase Leroys in rock. Yang also shot balls of lava at 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.
Yang made a cameo appearance in the Stitch! anime as an image on a computer screen. He later appeared in the special Stitch and the Planet of Sand.
- Yang was first revealed in a DVD bonus feature of Stitch! The Movie in the experiment gallery.
- An earlier, unused design for Yang was also shown in a promotional image for Stitch! The Movie.
- His name is derived from the concept of yin and yang; in this case his name stems from the force of yang, which is associated with masculinity, fire and heat, fitting his nature.
- Yang, along with Nosox, Richter, Butter, Splodyhead, Gigi, Tank, Shortstuff, Spike, Phoon, and one unconfirmed experiment, are the only known experiments that are primarily quadrupeds.
- Although Yang has been seen on his two hind legs, he is mostly seen on all fours.
- Yang is the only experiment besides Stitch to escape a net by himself.
- Yang's pod color is blue.
- Yang appears in the online game Lilo & Stitch: Alien Interception along with Plasmoid, Tank, Dupe, Clyde, and Hämsterviel.