- Not to be confused with P.J., a character from Goof Troop, A Goofy Movie, and An Extremely Goofy Movie.
PJ is incredibly silly and mischievous, even toward other experiments. As an expert prankster, PJ uses his intelligence to create ingenious pranks. As Lilo describes, PJ can be annoying with his pranks and while his pranks can be mean, he himself doesn't seem purposely malicious but merely carries out his programming. Like most experiments, he dislikes it when his goals do not carry through or are interrupted. He likes making people laugh with his practical jokes.
Experiment 133 was the 133rd genetic experiment created by Jumba with Hämsterviel's funding. He was designed to play practical jokes on unsuspecting victims, hence his name P(ractical) J(oker). 133 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.
133's pod was discovered by a man on the beach using a metal detector when it starting beeping. When he went to investigate, he uncovered an empty soda can with the experiment pod. He decided that the pod wasn't worth anything, so he threw it into the water, activating 133.
133, named PJ (for Practical Joker), then proceeded to play jokes on everyone he could find until he eventually ran into Lilo and Stitch. When PJ pulled many pranks on Stitch, the latter attempted to beat him up, only to be stopped by Lilo.
PJ was then taken back to the Pelekais' house, where Jumba claimed that PJ's jokes could result in mayhem. Regardless, PJ relentlessly pranked Lilo's strict substitute teacher for her hula class, while framing Lilo for it.
Later, Lilo wanted to play a spiteful joke on her harsh substitute teacher, despite Stitch's protests. PJ then pulled some more pranks on Stitch when the latter tried to capture him. However, Stitch eventually scooped PJ in a container so that he wouldn't cause further chaos.
When Stitch refused to allow PJ to help with Lilo's scheme, she used Drowsy to put Stitch to sleep and released PJ from containment for his assistance. PJ then cleverly formulated a plan to humiliate Lilo's substitute teacher with the ultimate practical joke.
Stitch later woke up on his own and triggered a booby trap set up by PJ, resulting in Stitch getting stuck inside PJ's containment orb. The next morning, Stitch was freed from containment by Pleakley. The former then rushed to Lilo's hula school, hoping to prevent her and PJ from executing their prank.
Meanwhile, PJ waited to unleash his practical joke on Lilo's substitute teacher, which ended up backfiring (due to Stitch intervening), and thus caused PJ to literally get his butt kicked (several times actually). Luckily, PJ was freed from his own contraption by a sympathetic Stitch.
Shortly after, PJ was found a one true place as an opening act performer for Moses' hula gig.
The first 624 experiments, including PJ, 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.
PJ participated in the following battle between the experiments and the Leroy clones.
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. PJ joins them for the song by playing the trumpet.
- PJ's pod color is white.
- PJ is described by the experiment computer screen as, "Experiment 133. Primary function: Farceur abilities."
- In the group photo taken at the end of Leroy & Stitch and the Disney.com Lilo and Stitch experiment gallery, PJ is not wearing his glasses. It is possible that the glasses got broken during battle.