In the majority of the franchise, Jimmy and Cindy share a huge rivalry in academics and physical abilities. Cindy was the smartest in her class before moving to Retroville, where she met Jimmy and the others. She lives across from Jimmy, whose intelligence put her at second place. Both being too prideful to acknowledge the other's individual skills and knowledge, these two young geniuses both strive to outdo the other. They have a love/hate relationship, due to their criticism and competitiveness toward each other, but secret admiration of each other along with it.
Though Cindy teases Jimmy and argues with him frequently, she does care about him and doesn't like it when Jimmy is sad, and often goes to comfort him. It is also shown that she wants to be as smart as Jimmy and she looks up to him.
Jimmy is understandably annoyed with Cindy's insults and teasing, but still sees Cindy as a friend because she's the one person who keeps him on his feet. Cindy tries to remind Jimmy of all the trouble he's caused and to think his plans through, but in his pride, Jimmy often doesn't listen to her and does what he wants instead.
By season three however, they are coming to terms with their feelings, and they slowly drop their rivalry. Cindy picks on Jimmy and his friends less, and Jimmy notices the change and begins to attempt at showing her that he returns her feelings. They slowly let go of hiding it from each other and get along whenever they're alone. By the end of the season, both of them acknowledged their feelings for each other and had begun dating, although they did try to keep it a secret and they pretend to argue in front of others. Cindy tries to get Jimmy's attention, but she gets angry when he takes credit for her ideas, ignores her and blames her for his actions.
If season four had been ordered, Jimmy and Cindy would've finally fully acknowledged how pointless pretending to hate each other was, ending their rivalry permanently.
Romantic Moments (in order)
- In the movie, when they're flying rockets, they turn to each other and exchange smiles. Later, when Jimmy starts crying, regretting his mistakes, she comforts him. At the end, she thanks him for saving everybody's lives.
- It is also worth noting that in the movie, she and Jimmy got along somewhat better than in most of the series until the end of season 3. In the cancelled season four, this would've been the case again.
- In a 2001 issue of Nickelodeon Magazine, a section had the characters' bios on it. On Cindy's bio, it said she was most likely to end up marrying Jimmy and Jimmy's worst fear was Cindy liking him.
- In a sneak preview for the series that aired during the 2002 KCA, there was a Q&A segment. One of the the questions was asking Jimmy if he and Cindy secretly liked each other. Some clips play of Jimmy and Cindy's positive interactions in the movie, and Jimmy then answers by denying liking her.
- In Normal Boy, Jimmy's intelligence is removed and he was no longer smart enough to think to hold back things he was private about, and so he tells Cindy he thinks she's cute. And of course at this point in the series, she's shocked that Jimmy thinks this of her.
- In Birth of a Salesman, Cindy tries to buy Jimmy from his parents when the Robot Salesman Willie Loman 3000 is bargaining him.
- Brobot, in his introductory episode, tells Cindy that he thinks Jimmy likes her. She smiles for a second before Brobot begins to tease. Jimmy denies the accusation, clearly embarrassed. Goddard, having taped all this, plays it to Jimmy at the end, which again embarasses him. He chases Goddard trying delete the video.
- In Granny Baby Jimmy is in charge of a baby, and Cindy offers to help him, because she says it needs her motherly care. For the rest of the episode, they basically assume parental roles toward the baby, and at one point Cindy even points out Jimmy being fatherly.
- In I Dream of Jimmy, Jimmy had to wake Carl from his dream by doing something in the dream that would surprise Carl enough to make him realize it wasn't real life. As soon as Cindy appears, he runs up and kisses her on the lips, and throws a disgusted face in Carl's direction after doing so, which did succeed in causing Carl to wake up. Jimmy later says to Carl that it was a "horrible desperate thing" he had to do, but acted very embarassed and guilty when Cindy approached him about it.
- In Trading Faces, while Carl, Sheen and Libby switch their memories back, they find a memory with a hilariously long line about one disliking the other and delete it because it's too confusing. By doing this, they unknowningly erase the spite one had toward the other due to being a show-off. When their brains are back to normal, Cindy mentioned one of them had daydreamed a romantic situation between them, including holding hands as they walk, then kissing. They both insisted they hadn't been the one thinking of that, but in order for them to both remember it, they both must have thought of it before, since neither could remember anything from the other's mind.
- In Safety First, she becomes concerned for Jimmy when he starts getting bullied by Terry Finster and tells him that he should tell a trusted adult about it.
- In Party at Neutron's, Cindy sees Jimmy and Betty dancing together and looks sad. She then remarks that she would never dance with Jimmy even if he was the last kid on Earth. Sheen then states she might be jealous and Cindy threatens to hit him in the mouth.
- In The Eggpire Strikes Back, when Cindy realizes that it's her fault Poultra got resurrected, she comes to Jimmy's defense. At the end, she and Jimmy dance together. He then wipes her memory of the entire day, despite her protest.
- In Beach Party Mummy, Jimmy carries Cindy on his back, and they exchange smiles. Also, when the light goes out inside the pyramid, Jimmy grabs Cindy somewhere (we dont see where), which makes her yelp, and she scolds him.
- During The Retroville 9, they embrace for a victory hug, then push each other away in awkward embarrassment. Later, Cindy (unaware that Jimmy has been cheating in the games) thanks Jimmy for coaching them.
- In Return of the Nanobots, Jimmy wrote a poem with the intention of breaking his robots by making them name all digits of pi. The poem references "I Sing the Body Electric" by Walt Whitman, saying "Cindy sings the body electric", meaning he thinks Cindy is beautiful. Also, at the end of the episode when everyone reappears, Jimmy catches Cindy as she appears in the sky. They smile at each other before he drops her.
- Love Potion 976/J has Jimmy accidentally exposed to a love potion, which makes him fall for Cindy. She doesn't know what he does in the episode is not of his own will. So when he asks her out she accepts, and even leans in for a kiss at the end of the date. Before they kiss, Jimmy quickly kicks her out of the lab and she looks genuinely hurt, believing that Jimmy was playing a cruel prank on her.
- In Send in the Clones, Romantic Jimmy serenades Cindy, who faints, thinking it's actually Jimmy. When everyone is telling Hugh what Jimmy's clones had done that day, she says Romantic Jimmy made her heart sing, but then quickly lies to cover it, saying he threatened her.
- In Billion Dollar Boy, Jimmy gets jealous when Eustace starts flirting with Cindy, who has developed a crush on him. Later in the robot fight, Cindy realizes that Eustace was just using her to hurt Jimmy, and then he forced Jimmy to watch Goddard die. When a heartbroken Jimmy thinks that Goddard has died, Cindy seems very regretful.
- In Foul Bull, Cindy says "If I ever get the hots for that idiot Jimmy, just lock me up!" which is her typical denial of her crush on Jimmy. Libby then calls her out on her statement, embarrassing her, which shows that Libby had caught on to Cindy's crush on him by this point.
- In The Science Fair Affair, Cindy makes sure Jimmy is banned from the science fair, to give other kids a chance at winning. But after the competition begins, Libby points out that she seems to feel guilty about getting Jimmy banned. She then puts her hand on Libby's mood reading CD player and it says that she misses Jimmy badly. Jimmy tries to cheer her up, but she hits him instead.
- In Win Lose and Kaboom!, they are trying to become better friends and nicer towards each other. Cindy tries to warn Jimmy about the consequences of answering the message on the space rock, but Jimmy doesn't listen and answers the message anyway. When Jimmy causes them to lose the first two events, Cindy tries to vote him off their team, for the sake of the planet and he attempts to do the same to her. Cindy tries to make amends later, but Jimmy brushes her off, unwilling to forgive her and Cindy reminds him that it's his fault the planets are going to be blown up. April the Gorlock appears to like Jimmy, who flirts back to her throughout the episode, which angers Cindy to the point of her challenging April to a fight. During the race, Jimmy accepts that he can't do everything on his own and finally trusts Cindy. He decides to be a team player and lets his friends help. After winning, Cindy and the others agree to help Jimmy save the other planets and stop Meldar. At the end, Jimmy and Cindy have a talk in the Candy Bar, settling the disagreements between them in that episode. They both lean in to kiss before an abrupt interruption, ruining their moment and Cindy angrily walks away.
- In Lights! Camera! Danger!, before the filming of a romantic scene between Jimmy and Cindy's characters, she accuses him of having planned it in order to kiss her. He argues that he hadn't, but tells her to make sure she does justice to the material and gives her a flirtatious smile and a wink. Jimmy smiles a little as he leans in, after Cindy had closed her eyes. Cindy fusses at Jimmy for pulling back, saying she had been in the moment.
- In The Tomorrow Boys, Jimmy and Cindy are married in the bad future, and Jimmy screams upon finding out. It is unknown if they will get married in their real future, since the futures shown by the Chrono-Arch are just predictions.
- During Stranded, they reveal some feelings to each other, after severely letting their guard down since they were alone, away from peers and competition. They spend all their time together while on the island. Jimmy gives Cindy a pearl, and they watch the sunset together. They often hold hands and flirt sweetly throughout the episode. When they are about to leave, Cindy begs Jimmy for them to stay on the island so they can be together, but they can't. At the end, they pretend to argue about Australia, just so they can go on a trip to Australia alone.
- In The N-Men, years of Cindy and her insults finally take a toll on Jimmy, causing him to turn into a Hulk-like monster bent on destroying everything in his path and insulting everyone. Guilty and admitting this is all her fault, Cindy decides to help Jimmy. When Cindy is dying after fighting Hulk Jimmy, she gets down on her knees, apologizes to Jimmy for hurting his feelings and tries to tell Jimmy she loves him, but then faints before she can get the words out. When Jimmy changes back to normal, he doesn't remember being turned into a monster. He tries to ask Cindy what happened, but when he sees that she's dying he quickly gets her and the others back to the lab and revives them.
- In Crouching Jimmy, Hidden Sheen, Cindy wanted to enter the school dance show with Jimmy but was discouraged when she heard him saying to Carl and Sheen that he thought it was lame. She tries to ask him anyway, and Jimmy accepts before she even finishes asking, although this was because he was worried about Sheen. She then becomes concerned about Jimmy's odd behavior when he, Carl, and Sheen leave, right after Libby mysteriously vanishes.
- In My Big Fat Spy Wedding, Cindy is frequently distracted by Jimmy's appearance and calls him handsome. During the wedding, she films Jimmy and says amorous things about him. When Carl and Sheen reveal Beautiful Gorgeous' plot, she is the first to help stop Jet from killing Jimmy. At the end of the wedding, Cindy catches the bouquet, looks Jimmy up and down and he smiles back flirtatiously before they both look away awkwardly and Cindy throws the bouquet to Carl.
- In One of Us, Cindy asks Jimmy several times what he was doing at Betty's house. She doesn't act angry like usual, but actually acts a bit sad asking. He repeatedly replies that it was nothing.
- In Vanishing Act, Jimmy's flirting with Betty pushes Cindy over the edge and she causes her, Jimmy, Betty, Carl, and Sheen to get sucked into another dimension. Later, she blames both of them for this, which makes Betty decide to pull Cindy aside and let her know she was aware of their feelings for each other. She told her to stay out of her face and that she can have him.
- In King of Mars, Cindy tries to flirt with Jimmy and gets angry when he ignores her, so she decides to form an alliance with Eustace, just to make him jealous. Jimmy then admits to her that the only reason he was pretending to ignore her was because she was distracting him, and also tells her that he thinks she's very smart and pretty. At the end, when all of them are in the ship going back home, he tries to deny the accusation that he likes her, which no one believes.
- In Lady Sings the News, Jimmy flirts with Cindy, and they are caught by Libby. To their embarrassment, their secret relationship is then revealed on live television. At the end of the episode, Jimmy kisses her for the first time, and they walk home holding hands.
- In League of Villains, Libby annoyingly says that Cindy is in love with Jimmy, but in her pride is unwilling to admit it. She reminds Libby that she feels the same way about Sheen, which she denies, but the girls then exchange a knowing look. In the lab, she sees that Jimmy has a lot of photos of Betty Quinlan, which she makes him get rid of. When everyone is about to be killed, Cindy stutters while trying to tell Jimmy she loves him. Jimmy rushes off to save them, but lets her know he knew what she was saying and kisses her on the cheek. When Cindy sees that they'll live, she takes back her words in embarrassment, after which she touches her cheek and smiles in his direction. At the end of the episode, he takes her hand as they walk into the Candy Bar together.
- Jimmy and Cindy's relationship is often compared to Arnold and Helga's from Hey Arnold, and Lincoln and Ronnie Anne's from The Loud House.
- Cindy's name was originally going to be Sally Proton. Jimmy's last name is Neutron. This may have been a clever hidden joke, because protons and neutrons are attracted to each other.
- Jimmy's favorite colors are the primary colors (red, blue and yellow) and Cindy's favorite colors are the secondary colors (green, orange and purple).
- In Out Darn Spotlight, Nick and Betty are cast as MacBeth and Lady MacBeth. Jimmy and Cindy getting jealous of this could be a reference to Jimmy liking Betty and Cindy liking Nick. It could also be a reference to Nick and Betty being distaff counterparts, like Jimmy and Cindy.
For images, see: Jimmy and Cindy's Relationship/Gallery.