She is designed to revert rehabilitated people and experiments to evil with a siren song, though it can have the opposite effect if it is heard backwards.
Also, experiments who were created after her, like Reuben, Stitch, and 627, are immune to her song.
She was captured by Gantu, but was rescued in "Snafu." Her one true place is with Lilo and Stitch as a pop star and singer. She speaks with a soft Scottish accent and is voiced by Tara Strong.
Angel is shown to be seductive and deeply enamored by Stitch. Sometimes she is good, and sometimes she can be downright mean.
Though since she has been turned good, her nice side shows a lot more. She has a very feminine voice and likes to flirt in front of the other experiments. She is 100% in love with Stitch.
She grabs onto Stitch and just tries to be near him at all times. She acts like a sister to both Stitch and Reuben, so she can be very protective of them.
She can and probably will get annoyed if she can't find Stitch or if someone is picking on her "brothers."
She acts more strict to Reuben than Stitch for reasons only she knows. She's always thinking of places she and Stitch can go and spend some time together.
She sort of acts like the mother to all the other experiments and doesn't mind showing it. She hates people who try and make trouble around her new home.
Lilo & Stitch: The Series
In "Angel," Lilo and Stitch were playing in the town when 624, named Angel, suddenly came out of nowhere and bumped into Lilo.
Earlier, Gantu acted like he was trying to capture Angel in order to lead her to Lilo and Stitch and trick them into taking her which was part of his evil plan.
Lilo scolded Angel and told her to watch where she was going, but the latter just growled at Lilo and fled.
Stitch, however, was smitten by Angel and chased after her. He soon found her in an alley and became attracted to her.
Angel then licked Stitch, who instantly fell in love with her. He tried convincing Lilo (who was suspicious of Angel) to let Angel stay with them.
Lilo eventually complied, but restricted Angel to sleeping in a basket instead of with Stitch.
During her stay, Angel began charming Stitch who developed a crush on her. Later, before Jumba could warn Lilo about Angel's powers, Angel sang into Jumba's ear, causing the latter to revert to evil and cover up for her.
After Lilo and Stitch left, Jumba allowed Angel access to his experiment database.
Unbeknownst to them, Angel was working for Gantu who had sent her to successfully seduce Stitch and lure him into a trap.
The next morning, Angel woke up to see Stitch proposing to her with a bouquet of flowers.
Angel was flattered by this, but then attempted to revert Stitch to evil as well.
However, this failed due to Stitch being created after her, although he complimented her singing.
Angel soon left the home with regret for Stitch and reported back to Gantu while reverting several rehabilitated experiments to evil along the way.
Confused but undeterred, Stitch pursued Angel around the island, and attempted to woo her in various ways.
She eventually lured Stitch to Gantu's hideout, where Gantu and the recaptured evil experiments lurked inside a concealed ship.
At the hideout, Angel revealed her true colors, but began to feel guilt over betraying Stitch.
When the now-evil experiments were about to finish Stitch off, Angel realized that she really did have feelings for him and turned the experiments back to good before Kixx could land the fatal blow.
The experiments then escaped the hideout while carrying Stitch triumphantly above their heads.
However, when all seemed well, Gantu captured Angel and fled with her, despite Stitch's best efforts to protect Angel.
In "Remmy," Angel was one of the experiments in Lilo's dream.
In "Snafu," Experiment 625 was able to trick the captive Angel into singing her song backwards (to "turn him good") while it was being recorded by him.
Gantu then planned to play the recording backwards on the island to revert all of the rehabilitated experiments to evil, but the plan failed due to Snafu stealing the recording.
Meanwhile, Lilo and Stitch launched a rescue mission on Gantu's ship, but were foiled by Snafu.
However, Stitch's love for Angel gave her the strength to break out of her containment orb and free Stitch and the others.
Lilo, Stitch, Angel, and the freed experiments then narrowly escaped the ship, and Stitch and Angel left on a date shortly after.