Yaarp, A.K.A. Experiment 613, is an illegal genetic experiment created by Jumba Jookiba. He is designed to create devastating sonic blasts from his megaphone-like antenna; he can also reduce these noises to soft, gentle honks. His one true place is at Lilo's hula school as an alien invasion alarm and buzzer.
Yaarp is basically very friendly but responds quickly and dramatically to the way others treat him. For example, if he feels intimidated or provoked, he will emit loud sonic blasts. If he feels safe or unthreatened, he will emit small, gentle honks as a sign of affection and friendship.
Yaarp, for the most part, is pretty simple and laid-back. However, he is very ready-minded and cautious but is loyal to those who win his trust. He is also a bit jumpy and nervous, sometimes sounding his horn at improper times because something trivial startled him. Aside from this, he can be quite easygoing.
Experiment 613 was the 613th experiment to be created by Jumba with Hämsterviel's funding. He was designed to use his sonic-blasting ability to shatter buildings and deafen nearby victims. 613 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 613's pod landing in Mrs. Hasagawa's fruit.
When Mrs. Hasagawa watered her fruit, 613's pod got wet, activating the experiment. After being admired by a couple on their honeymoon, 613 then caused massive chaos using his destructive shock waves.
When 613 was later chased into an electronics store by Gantu wearing special earmuffs, the former was captured in a container, but rescued and freed by Stitch. Instead of showing gratitude, 613 emitted a sonic blast that made Stitch go temporarily deaf, then fled the store with Gantu in hot pursuit.
Because Stitch was highly sensitive to 613's shock waves, Lilo hired Pleakley to try to capture the experiment. After Lilo, Stitch, and Jumba attempted to train and condition Pleakley, he was equipped with special experiment hunting gear.
Lilo, Jumba, and Pleakley tracked 613 down to a cave, while Stitch, using a conch, posed as the experiment and acted like a decoy. He then imitated 613's sonic blast to alert Gantu, who donned his earmuffs and pursued Stitch.
Meanwhile, a reluctant Pleakley entered the cave and discovered 613. When Pleakley unintentionally blasted 613 with a vacuum, the latter retaliated using a massive shock wave. However, when a sudden cave-in endangered 613's life, he was then saved by Pleakley. 613 was grateful and kissed Pleakley, who christened him Yaarp.
Pleakley and Yaarp then fled the crumbling cave and made it out safely. When Yaarp first noticed Lilo, he growled until Pleakley assured him that she was a friend, causing Yaarp to emit a gentle honk. Unfortunately, Stitch got captured by Gantu (who thought Stitch was actually Yaarp) during the process.
As part of a setup, Yaarp was taken to the local museum for a ransom exchange. When Lilo arrived with Yaarp in a pet carrier, the former made Gantu believe that Yaarp was rehabilitated. However, (as planned) when Gantu removed his earmuffs and bartered Stitch for Yaarp, the latter unleashed a sonic blast upon Lilo's signal, alerting the authorities and forcing Gantu to flee.
Yaarp, after being revealed to the mayor and chairwoman, was shortly after given a one true place as an alien invasion alarm at Lilo's hula school.
Yaarp reappeared in "Elastico" as one of the audience for Lilo's hula dance.
Yaarp reappeared in "Spike" as the scorekeeper for the Ohana-Rama. He was also briefly seen hiding under the couch during Pleakley's E.A.R.W.A.X. session.
In "Remmy", Yaarp was one of the experiments in Lilo's dream.
In the film's opening Yaarp can be seen greeting Lilo with sonic blasts from his megaphone.
Later, the first 624 experiments, including Yaarp, 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.
Yaarp 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 `Oe", which caused the Leroy army to shut down due to the original Leroy's fail-safe. Yaarp joins them for the song by playing the built-in horn on his head.
- Yaarp is one of the ten known experiments named by someone other than Lilo, the other nine being Gigi, Elastico, Hammerface, Thresher, Heat, Plasmoid, Morpholomew, Shrink, and Leroy.
- Yaarp was named after a word from Pleakley's home planet.
- Yaarp is capable of controlling the intensity of his sonic blasts, depending on how he feels around others.
- In "Spike", only Spike, Fibber, Nosy, Bonnie, Clyde, Slushy and Splodyhead were part of Pleakley's E.A.R.W.A.X. group, but in one scene, you can clearly see Yaarp hiding under the couch.
- Yaarp's pod color is yellow.
- Yaarp is described by the experiment computer screen as, "Experiment 613. Primary function: Noisemaker."
- Yaarp's torso and tail appear in the online game Jumba's Lab.