Bonnie is the brains of the duo. She is an obsessive and compulsive stealer of things. However, this doesn't stop her from being quite a helpful friend to others. Her closest partner-in-crime is Experiment 150, Clyde.
Bonnie has the qualities of a true, albeit amateurish criminal mind; being manipulative, cunning, streetsmart, and a great schemer. She is normally quite laid-back in situations (unless maybe the cops or other enemies are after her). With such a carefree, social, and almost friendly personality, it can be quite easy for the gullible to fall for her rotten tricks, namely Lilo and Stitch. Despite her deceptive, tomboyish nature, Bonnie can still have little etiquette and be very rude, as well as a bit short-tempered at times. She has an extremely close bond with Clyde, despite the fact that they have argued a few times before. She is naturally just seeking thrill, fun and adventure, even if it means stealing a few things or joining in on brawls with her other experiment "cousins".
She and Clyde are also seen to be hoarders as well as thieves.
Bonnie is a koala-like experiment with an hourglass-like figure and a large head. She has a yellow stomach, small antennae, dark blue eyes with eyelashes, two dark green marks on the back of her head, dark green arrow-like patches on her arms and legs, and a yellow V-shaped stripe on her forehead. She also has two fangs sticking out of her mouth.
Experiment 149 was the 149th genetic experiment created by Jumba with Hämsterviel's funding. She was designed to work with Experiment 150 to steal many belongings and evade arrest. 149 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.
149 and 150's pods eventually made their way into a supply of doughnut holes at Kiki's Coffee Hut.
Officer Kahiko, who was off duty, bought a bag containing two dozen doughnut holes at the coffee shack. He then took out 149 and 150's pods and (mistaking them for a new flavor) dipped both pods in his coffee, activating the two experiments, which proceeded to strip Kahiko and hijack his police car.
149 and 150 went on to cause countless robberies throughout the island until they were tracked back to their hideout by Lilo and Stitch, who had gone AWOL after being grounded by Nani earlier. After the four got acquainted, 149 devised a plan to encourage Lilo and Stitch's unruly behavior so that they would eventually show the two experiments how to break into Gantu's ship.
At first, Lilo and Stitch's naughty behavior posed as a distraction for 149 and 150 (named Bonnie and Clyde) while they stole from numerous places.
The following night, Bonnie and Clyde managed to convince Lilo and Stitch to help them successfully break into Gantu's ship. However, before the four could steal anything, they were ambushed and captured in containment orbs by Gantu. Lilo and Stitch were able to break out, though, and the four made a narrow escape.
When the outlaw experiments discovered that the police had found and secured their hideout, Bonnie convinced Lilo and Stitch to allow her and Clyde to take cover in the Pelekais' house.
Bonnie and Clyde attempted to hide in Lilo's laundry, but were discovered by Pleakley while the latter was taking out the laundry, prompting the two robbers to tie him and Jumba up and strip the house of everything. Jumba and Pleakley were later freed, and then let Lilo and Stitch use The Red One to chase down Bonnie and Clyde.
While the two thieves were fleeing to their new hideout in Nani's dune buggy – along with all of the Pelekais' other possessions in tow – they were attacked by Gantu in his shuttle, but saved by Lilo and Stitch, whom Bonnie and Clyde took back to their new hideout: the pre-robbed coffee shack.
However, Lilo and Stitch suddenly revealed their true colors: to re-infiltrate Bonnie and Clyde's hideout in order to capture them. When Stitch pointed a net cannon at the two crooks, Bonnie and Clyde attempted to escape out a window that was locked, but were blasted into a net by Stitch, handed over to Officer Kahiko, and sent to Kokaua Town Prison.
In "Spike", Bonnie was one of the experiments in Pleakley's E.A.R.W.A.X. group, alongside Clyde. When Fibber used his lie-detecting ability to prove that Bonnie was not as intelligent as she claimed, nor was Clyde at fault for getting them arrested, the duo got into a fight, which ended when Pleakley convinced Bonnie and Clyde to attempt hugging therapy on each other.
In "Snafu", Bonnie and Clyde were officially paroled, thus allowing them to join Lilo and Stitch on a mission to rescue Gantu's captive experiments. They assisted by opening a passage in Gantu's ship so Stitch and the others could break inside.
The first 624 experiments, including Bonnie and Clyde, 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.
Bonnie and Clyde 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.
Bonnie and Clyde made an appearance in the Stitch! anime where they escaped from Galactic Prison and traveled to the island in order to continue their primary function, which is theft. Because of this, they could be considered "incompletely rehabilitated." They have also revealed that they've tried to be good, but their programming interferes with it. Thus, it is unknown if they have truly turned good.
- Bonnie is Experiment 149. However, in her debut, she is called 349, most likely due to Jumba's untidy database.
- Bonnie normally has two fangs, but in "Spike", she has six fangs (four on the top and two on the bottom).
- Bonnie is named after bank robber Bonnie Parker.
- She speaks English like Reuben, but with a Mafia accent, much like the real Bonnie.
- She is also one of the very few known experiments that can speak English rather fluently.
- In "Spike", Bonnie was seen at Pleakley's E.A.R.W.A.X. group along with Clyde, but they were put in jail by Officer Kahiko. Though they could have temporarily escaped somehow.
- According to Bonnie's mugshot in "Snafu", her prison number is labeled 2734.
- Bonnie's pod color is purple.
- Bonnie is described by the experiment computer screen as, "Experiment 149. Primary function: Theft and evasion."