Princess Penny is the sixth episode of Stitch!-The Mischievous Alien's Great Adventure.
The episode begins with Penny wishing upon a star for her life to be better; in her eyes, everyone's mean to her for no reason and she doesn't deserve it (in reality, it's her who makes everyone else's life miserable). She wishes for everyone to see how wonderful she [thinks she] is.
The next morning, in Hamsterviel's secret asteroid base, Hamsterviel tells Gantu about his new plan: to use the recently stolen king-making Experiment 029, AKA Checkers, to enslave the planet. Reuben says he's coming along to stock up on sandwich ingredients while on Earth, but Hamsterviel forbids him to come and asks Gantu to apprehend him. Reuben dodges, though, and puts Checkers on his head. Both Gantu and Hamsterviel are then hypnotized by Checkers into believing that Reuben is their king. The sandwich-maker orders the two to clean up while he goes to Earth to do his shopping.
Reuben's spaceship lands on Izayoi Island. Yuna and Stitch see him and greet him when he arrives. He asks them to look after Checkers while he goes shopping. After he's gone, Yuna picks Checkers up in greeting, but the centipede-like creature slithers on top of her head. The shopkeepers around her all think she's a princess and offer gifts to her. She's creeped out by this but then figures out that it's Checkers' doing. She takes him off of her head and the spell over the shopkeepers is instantly broken. Stitch asks her why she stopped, and she answered that it wouldn't be right to take advantage of people like that. Checkers then slips out of her grasp and runs off. Stitch and Yuna pursue.
Penny and her entourage come across Sasha in town. The three boys try to flirt with her, but Penny just tries to insult her. Checkers then runs by and causes Penny to fall down. Yuna and Stitch arrive and the former asks Sasha if they'd seen a cute yellow centipede run by. Sasha points him out: on top of Penny's head. Within seconds, Yuna, Sasha, Kenny, Ted, and Marvin are all under the experiment's spell. The five start bowing to her and complimenting her, to which she is flattered. Stitch, being immune to Checkers' effect, asks for him back, but Penny refuses to give up her new crown. Stitch tries taking his cousin by force, but Yuna, loyal to Penny now, foils this plan. Out of options, Stitch runs away. Penny then parades through the town and soon every human on the island is hypnotized into obeying her.
While every human on the island is loyal to Penny, the three aliens, Stitch, Jumba, and Pleakley, aren't. After explaining the problem, Jumba attempts to come up with a solution. The doorbell then rings and Jumba goes down to answer it. Pleakley assures Stitch that the spell won't work on the two of them, but Jumba comes back up and declares his loyalty to the new princess. Pleakley resolves to fix the problem himself, but when he goes outside and encounters Penny (who had rung the doorbell earlier), he is quickly smitten as well. Stitch tries to reclaim his cousin again, but Yuna and Pleakley stop him. Stitch retreats again. Pleakley makes a fancy dress for Penny and servant garb for her brainwashed slaves and Jumba builds her a castle. After seating herself on her new throne, Stitch from overhead lowers a fishing line with a donut on the end. Checkers takes the bait, but when Stitch tries to pull him off of Penny's head, Yuna cuts the line. Stitch is captured and placed into a new machine built by Jumba, who explains that as punishment for treason against the "princess", his molecules will be randomly scrambled and transformed. The machine works and Stitch ends up turned into a pineapple with his face, arms, legs, and ears. Stitch runs out of the castle and Officer Suzuki, Mr. Honda, Tombo, Taro, and JJ all pursue him per Penny's orders, along with the threat of being turned into pineapples themselves should they fail.
The remaining servants attempt to prepare their princess a meal, but she rejects the healthy dishes and the people who prepared them are turned into sentient pineapples as well. The five who went after Stitch return and say that he got away, after which Penny makes good on her threat. Finally, she is satisfied with lots of dessert.
While all the tyranny is going on, Reuben's having a picnic on the beach by himself and enjoys sandwiches he made with actual sand in them. What appears to be a pineapple rolls down a hill next to him, but it's Stitch. The transformed experiment tries to explain the problem to his predecessor, but Reuben calms him down and offers him a sandwich. Stitch accepts, but there's hot peppers in it and he soars into the sky from the temperature. Reuben mentions that even Checkers might lose his grip with one of those sandwiches and Stitch decides to try it.
Back in Penny's castle, she's still eating dessert and starting to get bored. She overhears, Ted, Marvin, Grandma, and Ms. Kawasaki eating healthy foods and saying that they're glad to be doing so after all the sweet stuff. Penny quietly agrees with them, but Kenny and Pleakley see this kind of talk as treacherous and throw the four into the molecular scrambler. Soon, Yuna, Jumba, Pleakley, Kenny, Sasha, and Penny's mom are the only people who haven't been turned into pineapples. Stitch and Reuben secretly watch and the former instructs the latter to create a distraction so he can get to Checkers.
Penny starts to miss the way things were before; everyone is completely obedient to her, nobody will say anything negative to her, and Yuna agrees when Penny tries to insult her. She gives up being a princess and tries to pull Checkers off of her head, but he refuses to come off. Reuben appears and Yuna chases after him. With her gone, Stitch lands on top of Penny's head with one of the hot pepper sandwiches. But before he can give it to Checkers, he's grabbed by a giant mechanical hand from the molecular scrambler, which had been upgraded to be a juicer as well. Stitch is dropped in alongside Reuben, who had been captured. Penny yells that everyone is driving her crazy, but the servants respond by submitting to the same fate as the others, and Jumba places the rest of them into the scrambler/juicer as well. Penny remembers that Stitch was trying to get Checkers to eat a sandwich. She holds it up to him, but he doesn't take it. Reuben suggests tickling him, which works; Checkers opens his mouth to laugh and Penny shoves the firehouse special in. The temperature is too much for the experiment and he finally jumps off of Penny's head. The spell wears off on everyone and the're all confused as to what they'd been doing. Pleakley remembers that they're all about to be turned into pineapple juice, as does Jumba, but he can't seem to stop the machine; fortunately, it overloads and falls apart, leaving everyone all right. Penny's happy that her family's okay and back to their normal selves. Stitch asks Jumba when he'll be normal and he says to just wait for the affects to wear off. Reuben heads back to the base with Checkers in tow.
Back at the base, Hamsterviel's furious at Reuben for ruining his scheme, but the sandwich-eater puts him and Gantu under his control again with Checkers. Time passes, and everyone who had been turned into pineapples are normal again...except for Stitch. Mr. Honda delivers a package to him. It's another sandwich from Reuben; this one has even hotter peppers from another planet, and in a note included Reuben says that this may turn him back to normal. Stitch tries the sandwich and the temperature blasts him into the ocean. When he gets back on shore, he's back to his usual furry self! He gains a good deed for saving everyone on the island from Princess Penny (including Penny herself). Penny then approaches him and thanks him for what he did and says that she's [temporarily] a better person now. She gives him a pineapple as a memoir of the adventure. The episode ends with Stitch refusing and running away with Penny following and insisting that he take it.
- This episode marks the first second time Penny refers to an experiment by its real name. The second being Stitch, and the first being Angel.
- This shows how Penny perceives reality from her point of view.
- This is the first time someone has willfully taken Checkers off of their head.
- Deleted scenes from the Japanese dub:
- After Stitch tells Penny to thank Checkers, she is confused, but then freaks out when she sees him, in which Yuna explains his powers before Kenny calls Penny a princess.
- The scene of Stitch saying that he will take Checkers to Jumba and Penny protesting was cut out from the Original Dub.
- Penny never refers to Jumba or Pleakley by name, but in the Japanese dub, she does.