Lilo and Stitch are wandering around Kokaua Town looking for stuff to add to Lilo's "slug circus" when they suddenly see Gantu supposedly looking for an experiment. As Stitch takes care of Gantu, Lilo suddenly bumps into a pink female experiment that looks a lot like Stitch. The experiment growls at Lilo and flees, and Stitch spots the experiment from a distance afterwards. After he chases the experiment into an alleyway, she charms him and licks his face, making him instantly lovestruck with her. Despite Lilo being very suspicious of this experiment, Stitch convinces Lilo to take the experiment home with them.
As Stitch spends some time with the experiment, numbered 624 and sarcastically named by Lilo as "Angel", Lilo tries to ask Jumba about what the experiment's function is. However, when Stitch and Angel come into Jumba's bedroom, she sings into Jumba's ear, causing him to become evil again and lie about her functions. Once Lilo and Stitch leave, Jumba lets Angel access his experiment database.
Overnight, Angel wakes up from her laundry basket bed in the Pelekai residence (Lilo wouldn't let her sleep with Stitch) and sneaks over to Gantu's ship, revealing to the viewers that she was working for him and Hämsterviel. Gantu sent her to seduce Stitch and infiltrate the Pelekai household. 625 also tries to woo her, but she is completely uninterested in him.
The next morning, with Angel back in the basket, Stitch wakes her up carrying a bouquet of flowers. Although flattered, she tries to revert him to evil. To her surprise, however, her song has absolutely no effect on him, although he does compliment her "nice pipes". She then leaves the house with regret for him and goes out to revert several rehabilitated experiments back to evil. As she converts them, Stitch tries to win her back by doing several nice gestures for her, but none of them seem to work. At night, Angel has Stitch follow her up Mount Waialeale, luring him into a trap.
During this time, Lilo eventually finds out about Angel and her true motives. Thanks to Pleakley having followed Stitch and Angel throughout the day, recording their love story with a powerful handheld digital camera, Lilo realizes that Angel was working for Hämsterviel through a Ridiculously Long Phone Number on a dog tag the experiment was wearing. Likewise, Jumba tells Lilo about Angel's function. Lilo takes his computer and plays a recording of her song in reverse to revert him to his previous Affably Evil self.
Lilo, Jumba, and Pleakley then head to the summit of Waialeale, but by then they were too late as a spaceship hidden underneath the mountain blasts off. Inside the ship, Angel reveals her true motives to Stitch and traps him inside. Gantu then sics the captured experiments that she made evil again on Stitch. Stitch tries to destroy the ship's navigation systems, but the systems are protected by a force field. He gets shocked and weakened by the force field, leaving him at the mercy of his cousins. Feeling immense guilt for betraying the first person who ever treated her with genuine kindness, Angel sings her song backwards, restoring the experiments back to good before they could knock Stitch out. The experiments then turn on Gantu and destroy the navigation systems, bringing the ship crashing back down to Earth.
After the experiments leave the ship, Lilo realizes that Angel saved Stitch's life and finally accepts the experiment into the 'ohana. Unfortunately though, Gantu, angered by Angel's betrayal, blasts Stitch into a net and captures her in a capsule, running off with her before Stitch could free himself. Stitch is saddened by losing Angel, but Lilo promises him that they will rescue her someday, which they will eventually do so in late Season 2.
Experiments who appeared or were mentioned in this episode:
- Sparky (X-221): One of the experiments that Angel reverts to evil. After he returns to good, he disables the force field around the spaceship's navigation system.
- Yin (X-501): One of the experiments that Angel reverts to evil.
- Yang (X-502): One of the experiments that Angel reverts to evil.
- Richter (X-513): One of the experiments that Angel reverts to evil. When he does so, he starts causing earthquakes again, which brings down Stitch's sand sculpture of Angel. After he returns to good, he breaks the glass surrounding the spaceship's navigtion system.
- Cannonball (X-520): One of the experiments that Angel reverts to evil.
- Slushy (X-523): The first experiment that Angel reverts to evil. When he does so, he abandons his post at the Shave Ice stand and starts freezing Kokaua Town again, which affects Stitch and causes his Sweetie Graffiti watermelon to break apart.
- Kixx (X-601): The last experiment Angel is seen reverting to evil. When he does so, he starts attacking beachgoers again. Stitch sees this and knocks him out with a solid uppercut. On the ship, he almost lands the fatal blow that would have taken Stitch out had Angel not reverted Kixx and the other experiments back to good.
- Angel (X-624): This episode's Monster of the Week; a pink, female Stitch-like experiment whose primary function is to turn any reformed experiments (and Jumba) back to evil by singing a song, although this can be reversed if she sings backwards or her song is played in reverse. Her song has no effect on the experiments made after her. As noted, Stitch falls in love with her, and she eventually falls in love with him.
- Reuben (X-625): He is also enamored by Angel and calls her "Hotcakes", but she doesn't share the same feeling towards him.
Tropes in this episode include:
- An Aesop: You've got to believe in love.
- The Bad Guy Wins: In a way; although Gantu fails to bring the experiments directly to Hämsterviel, he does capture the reformed Angel, preventing her from staying with Stitch. 625 even says, "Bad guys win!" as he and Gantu run off.
- Blatant Lies: After being converted to evil by her siren song, Jumba describes Angel as a "harmless early experiment designed to pop popcorn for Jumba's movie night." While repeatedly referring to her as Experiment 624.note
- Breaking the Fourth Wall: Once the re-reformed experiments turn on Gantu after Angel converts them back to good, Reuben says, "Uh-oh, plot twist."
- But for Me, It Was Tuesday: Gantu's personal Offscreen Moment of Awesome where he managed to capture Angel (not the capture we see at the end) apparently happened on the previous Tuesday from time of the episode.
- Continuity Nod:
- Stitch picks his nose with his tongue in this episode, just like when he did so in the original film. Surprisingly, when he does this in front of Angel, she gets intrigued enough that she picks her own nose with her tongue.
- Likewise, Stitch introduces himself to her with the same awkward, prolonged "Hi!" with squinting eyes, outstretched arm, and bared teeth upon meeting her face-to-face, just like he did with Lilo when they first met.
- Stitch takes a girlish, Big Wheel-styled tricycle from the streets to chase down Angel at the beginning. It's practically the same model trike he took from Mertle Edmonds when he tried to look for a city on Kaua'i back then.
- Damsel in Distress: Angel becomes this at the end of the episode.
- Defecting for Love: Angel ends up regretting her actions when Stitch was about to be pounded by his cousins. Thus, she sings her song backwards, reverting the experiments back to good and proving that she is done working for Gantu and Hämsterviel.
- Downer Ending: One of the rare times in The Series where this happens. Angel saves Stitch by turning the experiments back to good, but her now-former boss captures her in retaliation. Lilo and Stitch do resolve to save her one day, however, and eventually do so at the end of The Series.
- Enhance Button: How Lilo was able to make out the details of Angel's dog tag in Pleakley's video recording of her. Justified as the video camera Pleakley was using was made by Jumba and can record at an insanely high resolution.
- Evil Diva: What Angel is at the beginning, and her song can cause an experiment made before her (and Jumba) to do a FaceHeel Turn.
- Face of an Angel, Mind of a Demon: Angel's personality before she reformed and also the basis of her name, which is most likely inspired by "(You're the) Devil in Disguise".
- First Appearance: Take a wild guess.
- Girls Have Cooties: Stitch initially finds love to be "icky" and is dismissive of Pleakley saying that Stitch will find someone like him someday. Needless to say, he quickly changes his mind when he meets Angel.
- The Immune: Angel's singing has no effect on Stitch and 625 because they were created after her.
- Ironic Nickname: Invoked by Lilo's naming of Angel. This stops being ironic after Angel redeems herself.
- Love at First Sight: When Stitch sees Angel's face for the first time, he instantly becomes smitten with her. Granted, she intended for this to happen once she was cornered.
- Love Redeems: How Angel was reformed instead of Defeat Means Friendship.
- Moment Killer: When Angel is about to go to bed she gives Stitch a look that says "come to bed with me" and Stitch is all too eager to, but then Lilo makes them sleep in separate beds.
- My God, What Have I Done?: Angel clearly shows this reaction when Stitch is about to be pummeled by the experiments she made evil again.
- No-Sell: Angel is dismayed to find that her siren song has absolutely no effect on Stitch. He does compliment her singing, though.
- Recycled Premise: This episode's plot shares a few similarities with the original film. A genetic experimentnote takes advantage of another being who cares for them,note only to develop feelings for said being after spending time with them. When the other being gets captured by Gantu and trapped in his spacecraft, the experiment saves them from him and destroys his ship, redeeming themselves and truly becoming good. In the end, however, the experiment gets captured again.note The main differences are that Lilo and Stitch's relationship is platonic while Angel and Stitch's relationship becomes romantic, and that while Stitch was allowed to stay with Lilo, Angel was taken away from him and had to be rescued later.
- Ridiculously Long Phone Number: Hämsterviel's phone number is 5550198293434533655882.
- Sweetie Graffiti: This episode provides the trope page's image. Stitch carves his and Angel's experiment numbers ("626 + 624") within a heart on a watermelon. A re-eviled Slushy freezes Stitch and the fruit, which causes it to break apart.