In the movie, shorts and season one, Libby wore a green dress with blue and orange patterned rectangles on it, green knee high socks, and black shoes. She also had a streak of her hair covering her right eye along with her hair in a high bun.
In "Beach Party Mummy", Libby is given a new hairstyle (Egyptian dreads to be exact) as part of Jimmy's plan to make Libby look like her ancestor, Queen Hasabataslapya and put the mummies to sleep for 10 trillion more years. Libby likes the hairstyle so much that she decides to keep it. In the next episode, Libby gains new clothes; a striped pink fading shirt, blue jeans, a blue collar and brown shoes.
She also wore a purple shirt, white pants, and white shoes in "Nightmare In Retroville" for her fashion model Halloween costume and while she was a werewolf. She also wore this in Lady Sings the News.
She was seen in her underwear for the only time in "Patrick the Snowman." It is two pieces and consists of the same color scheme of her dress.
Not much is known about Libby's family, but she is known to have a father and mother. In "Beach Party Mummy," she discovers that she is related to Queen Hasabataslapya, and changes her hairstyle to the one her ancestor wore in her portrait.
In the shorts, movie and early episodes, Libby was more of a sidekick towards Cindy, but as the series progressed, she became more of her own character and evolved into Cindy's voice of reason.
Libby's main interest is music with a funky rhythm. When she experiences music withdrawal, she faints and goes crazy. She also loves electronic gadgets and being stylish. In the first season, she doesn't appear in the title logo. When she becomes more involved in the show, however, she is added to the logo in the third season. Unlike Jimmy's other best friends, Libby is shown to do well in school, and is even on the same level of Jimmy and Cindy in terms of intellect.
Her favorite band is Graystar whom she sometimes asks to play at Retroville. She is also revealed to have piano playing skills.
Along with Cindy, Libby won a first place trophy for river stomp dancing at the school contest in "Battle of the Band;" Jimmy, Carl, and Sheen almost beat the girls with their electronic rock music guitars and drums, but at the last minute, Carl and Sheen destroyed their own instruments in a jealous quarrel, and the boys ended up with was an eighth place trophy after Carl did his giant snot bubble trick.
Libby has full knowledge about Jimmy and Cindy's relationship with each other, as Cindy does not want to express her feelings to Libby about it and stammers each time Libby mentions it. Although, Libby sometimes joins Cindy in teasing Jimmy. Libby returns Sheen's interest in herself, but not when Sheen is not annoying her with his overbearing mentions of Ultra Lord and occasional flirting.
In "The Tomorrow Boys", Libby had become the evil dictator of Retroville after Carl accidentally got the Megalomanium to her birthday party out of confusion by the perfume and the Megalomania. When she opened the present, she became mad with power, thus making her the evil dictator of Retroville. When Jimmy, Carl, Sheen and Goddard saved the future, she got mad at them for destroying her gifts and runing her party. When Sheen explains everything and apologizes, she forgives him and realizes how much Sheen cares about her.
In "Crouching Jimmy, Hidden Sheen", Yoo-Yee kidnaps her, so he can take Sheen's place as the Chosen One in Shangri-Llama. Sheen goes to rescue her and defeats him after Libby admits to being his girlfriend. Libby also realizes that Sheen cares about her more than Ultra Lord. It is also shown that she cares about him more than music.
In "The N-Men", Libby gains the super power of invisibility, based on how she was putting on vanishing cream for her acne when she and the group were exposed to the Van Patten Radiation Belt. Libby calls herself "Invisible Sister". She learned in the military station that she also had the ability to generate a force field, and create a pad to float herself in midair.
In The League of Villains, Jimmy, Carl, Sheen, Cindy and Libby's superpowered have been mixed up. Libby is the one who had ended up with Carl's superpower; Burp Boy. This made her gain the ability to make gigantic burps enough to make anyone go flying.
But of course, despite this, Libby is smart enough to know that even some of Cindy's own absurd antics warrant a snide remark or a slight hint of disappointment from Libby (making her a bit of a foil), especially since she is well-aware of Cindy and Jimmy's feelings towards each other.
In the shorts, the movie and season one, Libby was more of a sidekick to Cindy and didnt have much of a role in the franchise, but since Beach Party Mummy, she's become more of her own person and Cindy's voice of reason.
Libby and Sheen weren't quite close friends at the beginning, however Libby does encourage and compliment Sheen when he comes up with a good idea. For instance, in Beach Party Mummy, when Sheen distracted Principal Willoughby by telling him that new school tanning salon had been opened, Libby smiled and responded to Sheen's idea with "Great thinking Sheen!" The two were even seen dancing alongside each other in the same episode. Libby also always sticks up for Sheen whenever somebody yells at him or mocks him. A good example is at a scene in the Yolkian dungeons in the movie.
Their friendship eventually blossomed into a relationship during the episode of Love Potion 976/J, where Sheen was accidentally exposed to Jimmy's love potion and suddenly fell in love with Libby. From then on, Sheen has shown interest in her and is always looking after her, but it is hinted in previous episodes that he's always liked her. While Libby doesn't always approve of the nicknames which Sheen makes up, she returns his feelings and thinks he's cute and funny. In Crouching Jimmy, Hidden Sheen, she finally becomes Sheen's girlfriend after defeating Yoo Yee. We also learn that Sheen actually cares about her more than Ultra Lord and that she cares about him more than music.
In Planet Sheen, Sheen gets a new love interest and his and Libby's relationship is abandoned because of it. It is unknown if they were still together or broke up at that point.
Brittany often appears as a third member of Cindy's circle of friends, usually for singing, dancing or just for hanging out. One time, Brittany bribed Libby into being her science partner with a shiny new CD. While Libby and Brittany don't hang out as much as she and Cindy do, they're very good friends and get along well.
Libby plays the role of a big sister to Jimmy and is always trying to get him to come out of his shell. Jimmy likes Libby because she's calm, mellow and sensible.
In Crouching Jimmy, Hidden Sheen, Yoo-Yee thought Libby was Sheen's girlfriend, so he tried to kidnap her to urge Sheen coming to Shangri-Llama and fight him. He tried to be nice to Libby, and even gave his sister's room to Libby, but she didn't like it because her CD collection was totally beat and hated the wallpaper. However, Libby did like Yoo-Yee's sister's jewelry. She was also angry at Yoo Yee for beating up Sheen, which gave Sheen the proper motivation and made him defeat Yoo Yee.
- "Keep yellin' if you wanna mirage slappin in yo FACE!!" - Stranded
- "Sheen, none of those things do any of those things..." - Stranded
- "You can't stop da' funk...ya mamma can't stop da' funk--AH AH--yo brotha' can't stop da' funk..." - Stranded
- "Give it up for JIMMY!!! We believe in you, Jimmy!" - The Eggpire Strikes Back
- "Open your EYES, girlfriend! I'm right in FRONT o' you!!" - The N-Men
- "We hafta WHAT?!!" - Substitute Creature
- "Why don't we just go after the dog??" - Jimmy Timmy Power Hour
- "But my mama told me not to burp in public!!!" - The League of Villains
- "Ladies, there's this spanking new band called Graystar and all I'm asking you is to stop walking away while I'm talking to you!!!" - Attack of the Twonkies
- "Yeah, or we could play 'Spin-Sheen-and-hit-him-with-a-bottle'." - Party at Neutron's
- "Meet me at the Candy Bar, Sheen, (opens door) AFTER YOU CLEAN MY HOUSE!!" - The Tomorrow Boys
- "How come I'm not invisible? (burps explosively) (covers mouth in embarrassment) Excuse me. (explosive belch) Ugh, I'm Belch (explosive burp) Boy?! (loud burp) This is way embarrassing." - The League of Villains
- "Sheen, you better put some hurting on this fool! You hear me?! This is your girlfriend talkin' to you!" - Crouching Jimmy, Hidden Sheen
- "Wait, stop! Carl's not an alien!" ... "What?! Oh, no!" ... "Forgive me, guys?" -Lady Sings the News
- "I was listening to a good song; I have priorities." - The Retroville 9
- "Get your tounge off the floor." - The Great Egg Heist
- "Hey, Cin, put your eyes back in yo' head and let's get to work."-My Big Fat Spy Wedding
- "Here we go, here we go." - Movie
- "100 years of hard labor!" - The Tomorrow Boys
- "Do you have some carrot sticks or maybe some antacid?" - Hypno-Birthday To You
- Libby is one of two females in the franchise to burp, the other one is Judy.
- She is eleven years old (twelve starting with "The Tomorrow Boys").
- Libby is the second protagonist in the franchise to become evil. The first one was ironically Sheen.
- It is unknown why Sheen doesn't mention her or bring her up in Planet Sheen or if they were still dating at that point.
- Libby's bad future counterpart looks more like her original design than her current one.
- While Libby loves music, she calls Yoo-Yee's sister's CD collection totally beat.
- Libby has a little brother (who's name has not been mentioned and looks was unseen in the series) seen in the beginning of "Make Room for Daddy-O" as the legs in the saw the lady in half trick.
- Sometimes, it is hinted that Libby may like Ultra Lord too.
Main Characters: Jimmy Neutron | Carl Wheezer | Goddard | Sheen Estevez | Cindy Vortex | Libby Folfax | Nick Dean | Goddard | Hugh Neutron | Judy Neutron