Lisa, despite her very young age, is a Junior Nobel Prize recipient. Though she is still in first grade (kindergarten in the first four seasons), she is exceedingly smarter than the other kids her age and is shown to be capable of moving up at least six grades.
The comic "It's Just a Phase" reveals that she started doing experiments at around age one, but it was believed by her parents to be "just a phase." The comic also reveals that back then, her outfit consisted of her glasses, a green T-shirt, a white lab coat, a diaper, and pink booties.
Though the second-youngest of the Louds, Lisa is a child prodigy, so she's the smartest kid in the bunch. Because of this, she often tends to be egocentric, boorish, condescending, and sarcastic with other people. She speaks with a lateral lisp, and usually has a stoic frown, though she does smile from time to time.
She is not as easily-excited as her siblings, although sometimes she becomes excited when something really good happens, like when she and the other sisters discover Lincoln's romantic situation in "Heavy Meddle". She states that this is because she does not partake in "mundane human emotions", which she first stated in "Heavy Meddle". She was also shown to have fallen for Hugh like all of her other sisters, and showed a more immature side to her, at one point having Hugh show off his six pack under the lie that she was teaching Lola human anatomy with him as an example. She also became somewhat irrational, claiming she would marry Hugh, and have children with him, despite the obvious age difference, and following him around like her other sisters. She also does not believe in superstition, fortune telling, blessings or curses as she is a realist and believes only in science as stated in "Raw Deal" and "Study Muffin". However, she isn't completely close-minded, as she believes in aliens, as she claimed in "Friend or Faux?", and she accepts the fact that Luna is dating a girl, as seen in the comic "Sam's Pick". Nonetheless, she likes to be with her siblings and have fun with them, even if she doesn't express it.
In many episodes, she can be seen working on strange experiments. In "Left in the Dark", she creates an Oreo shaped cookie called "Gloweos" with the infused DNA of a jellyfish, and if someone ate it, all of his/her body would glow. One of her favorite hobbies is resolving very difficult math problems. She also likes to study the poop and bathroom habits of her siblings, something they all find gross and annoying.
As seen in "Overnight Success", Lisa not only likes to do experiments on her siblings, but she also likes to do them with people outside of her family.
Though easily the most mature of her siblings, she can also be quite mischievous and sneaky. For the most part her pranks are hidden in unassuming objects; such as acne cream, sunscreen, mouthwash, etc., with results like turning skin blue, mild sunburns, and hot-pepper induced fever, respectively. Lisa is also completely willing to join in the madness caused by her siblings, whether it be disputes over money, the "sweet spot," or just playing along. This proves that while Lisa is a genius, she's still a kid and occasionally acts her age.
Contrasting most of her family, Lisa is very honest and blunt about what is on her mind. Lisa's brutal honesty isn't so much out of a sense of morality, but because she doesn't want to waste brain space by making up a lie. However, in "House of Lies", she is shown to be horrified by the number of lies in her house, and even tries to remedy it, implying that her honesty is at least partially due to a sense of morality. As seen in "Heavy Meddle", her honesty makes her incapable of keeping a secret. Like Lincoln, she's very individual in contrast to rest of the sisters as seen in "It's a Loud, Loud, Loud, Loud, House".
Lisa, like her polar opposite Leni, is ironically very scatterbrained. She can frequently forget crucial ingredients to her various experiments, which can lead to devastating, though hilarious, outcomes. She also frequently forgets to look up while reading while walking, much to her embarrassment, and tends to misplace her vials, test tubes, and chemicals.
As seen in "Party Down", Lisa appears to have a fun side, as she gets what appears to be a sugar high from having too much chocolate from a chocolate fountain. This proves that Lisa isn't a complete no nonsense person and can loosen up and act her age.
In the episode "Friend or Faux?", she is shown to be very manipulative, as she manipulated an innocent girl named Darcy Helmandollar into befriending her just to get an "A" in social skills. Despite this, when Darcy felt bad after discovering Lisa's ulterior motives, Lisa felt guilty, showing that she does not manipulate people out of ill intent.
"Lisa Loud is smarter than the rest of her siblings combined. She spends most of her time in her lab setting off mysterious explosions, but she's always willing to help out with homework, or explain the structural flaws in someone's pillow fort. She loves her test subjects siblings!"
Lisa wears a short, shaggy, brown wig and large glasses. She wears a green turtleneck sweater, dark pink pants, and brown shoes with no socks, all of which droop down to illustrate her stoic demeanor.
Her sleepwear includes a lime green nightshirt with matching pants. Her swimwear consists of blue goggles, and a green one-piece swimsuit with a horizontal pink line in the middle.
"Potty Mouth" reveals that she is actually bald and toothless due to her experiments. Because of this, she wears a wig and dentures. In addition, she has an extra toe on her right foot.
Lisa's glasses are black-framed, with two circular lenses that are a translucent blue color, and only her pupils can be seen through them when she is wearing them. As of "Making the Grade", she has surgically corrected her eyes, and no longer needs them to see. However, she still wears them for unknown reasons, possibly a subconscious reaction as she has worn them her entire life.
In an alternate universe where the sisters are boys, Lisa is a boy named Levi. Like Lisa, Levi is a child prodigy, and speaks using really big words, as shown when he told his two older "cro-magnons" Leif and Lexx (Lana and Lola) to diminish their cacophony, so that their youngest sibling can suspend consciousness. But, being only six years old; Leif and Lexx had no idea what Levi was saying. So, they just ended up telling Levi to "speak English." To make it easier for Leif and Lexx to understand, he said, "Shut your pie-holes so Leon can nap!"
Unlike Lisa however, Levi is shown to be harsh and uncaring towards Lincoln, as shown when the boys mock him after Luke (Luna) uses him to clean the bathroom, laughing at him when Leon bit his thumb when he got a "boo boo", and teasing him over going on a date with Ronnie Anne. He is also harsh towards Lynn Sr., as the boys dog-pile him whenever they see him. He also plays keep-away with the time watch his female counterpart made to send Lincoln home.
In another alternate universe where everyone is the opposite gender, and Lincoln is a girl, Levi is shown to be caring and honest with Lincoln, like Lisa.
Levi eventually ceases to exist, when it is revealed Lincoln's whole adventure with the boys was just a really strange dream he was having.
In the minicomic Deuces Wild!, Lisa interprets the superheroine called Card Counter, who is also one of Ace Savvy's sidekicks. She uses a special container to trap creatures like the gas monster. In the comic, she is summoned by Savvy (played by Lincoln) alongside the rest of Savvy's deck (played by the rest of her sisters) to help him and One-Eyed Jack (played by Clyde) to defeat the gas monster. After they defeat it, they prepared to fight against a garbage monster. This was a fantasy Lincoln had based on him, Clyde, and his sisters changing Lily's diaper and taking out the trash.
In "Pulp Friction", Lincoln comes up with the Card Counter as part of a comic he wrote to enter in a contest.
In "Kings of the Con", Lisa goes to a convention dressed as the Card Counter and impresses everybody, especially when she wins a counting competition.
Beatrice is the one of the rabbit sisters, and the rabbit version of Lisa Loud.
Beatrice is a standard white rabbit, with a pink nose, that wears a chartreuse top with a light blue collar, and a light blue colored skirt. She also wears big thick black glasses.
Beatrice is like Lisa in every aspect: she's the smartest member in the family, and has a lateral lisp.
This unnamed robot is a robot that Lisa based on herself in the children's story they made up in "A Dark and Story Night".
The robot is silver and runs on a track. She has large yellow eyes, grey arms and fingers, a little blue door on her belly, a large head, red markings on her body, and an antenna with a red light on top. She also wears a red sports helmet and black glasses. The robot Lisa is usually quite small, but she has the ability to grow larger.
In the story, the robot Lisa was trapped in a bramble bush and freed by Triton (Lincoln's alter-ego), DeLola (Lola's alter-ego) and Ribbon (Lana's alter-ego). The robot explained that her battery was low and she needed recharging before sunset, so she accompanied them on their quest for pieces of an electric crystal.
Later, she helped the mermaid version of Lori by building a waterwheel for the mermaid to charge her phone with.
When the crystal was assembled, the robot Lisa recharged her battery, grew larger, and hugged everyone else.
Lisa is skilled at breakdancing, as shown in "Tripped!".
For a long time it was thought that Lisa was the first Loud sibling to have their middle name revealed, in "April Fools Rules", where it's revealed that her middle name is Marie. However, it could be false because according to the "Ask Lincoln" segment in Instagram, their parents calls everyone Marie as a second name when they are in trouble.
Lisa does not use the bathroom, because it steals time away from her experiments, and instead uses her roommate's training potty. However, this seems to have changed before "Spell It Out", because in that episode, she does indeed use the bathroom.
She has a habit of giving the scientific name of an event or object, then calling it by its "street name".
She prefers to sit in the back of the car in case the engine blows up or a low flying plane comes in.
The episodes "Linc or Swim" and "Suite and Sour" suggest Lisa is fastidious about hygiene, as she is seen constantly trying to check in whether a pool she's about to enter is clean. "Wet, Lather and Scrub" also suggests that she is fastidious about hygiene, since she reminds kids to wash their hands, washes her whole body several times, and expresses disgust at her classmates' unhygienic habits, referring to them as "walking petri dishes."
Lisa has already finished school up through getting a PhD, but in "Making the Grade", she's suddenly attending Lincoln's elementary school.
She does not mind doing Lori's homework, but does not appreciate how it is not "challenging" enough for her to do.
Luna ruined Lisa's first opera by stage diving onto the orchestra.
This also reveals that Lisa likes opera.
Lisa's ideal superpower is her brainpower, claiming she does not need one.
Her Polish name is Halszka, with the nickname "Hala."
Lisa tutors Lynn to allow her to stay on her sports teams.
It is also revealed in "Study Muffin" that Lisa tutors all of their other sisters. She does not tutor Lincoln because she does not have the time to, although she apparently would tutor him if she was able to.
It is confirmed in "Picture Perfect" that she is almost blind due to astigmatism and cannot see very well without her glasses.
In the comic "Shocker", Lisa has the ability to understand Lily's babbling.
This means that Lisa, Lincoln, and Luan are the only ones who can understand Lily's babbling.
Another comic, "It's Just a Phase", reveals that Lisa started doing experiments when she was one, which was initially dismissed as a phase by Rita and Lynn Sr.
She talks to the audience in "Undie Pressure", making her the first character besides Lincoln to do so.
She is the second-youngest, but the most intelligent of her siblings. Alternatively, Leni is the second-oldest but the least intelligent of her siblings.
According to "Party Down", she can get really hyped up on sugar.
It is revealed in "Spell It Out" that Lisa has spent 1,482 days in her lab, which equals to 4 years and 22 days. This means that she has been a science genius since her very birth.
Lisa can sometimes be very immature and disgusting. As seen in "Study Muffin", she shows Lola Hugh's six pack and butt, and in "Lock 'n' Loud", she installed cameras in the bathroom, and she asked Lori and Leni for their stool samples.
Lisa does not always get permission for her experiments. For instance, in "Room with a Feud", Luan asks Lisa how she got their DNA samples and she doesn't want to answer, in "Project Loud House", she tricks Leni into using her experimental ointment, and in "Undie Pressure", she runs into the bathroom while Lori is using to complete her scatology.
Due to a "nuclear experiment gone wrong," Lisa is bald and has to wear a wig, and also has an extra toe on her right foot. Lisa is also revealed to wear false teeth, but it is never explained how, other than Lisa simply telling her siblings that it is a "long story."
However, the info about Lisa's hair and feet has been contradicted a few times in previous episodes, such as "Room with a Feud", when she is scratching her head, only to have her hair fall off, as if it was attached to her. Also, in episodes where she is shown barefooted, she does not appear to have an extra toe on either foot.
In "The Mad Scientist", while making sure she has her eleven toes after going back in time, it's also revealed near the end of the episode that Lisa also does not wear socks on her feet while wearing her shoes.
In "Potty Mouth", it is shown Lisa likes rap/hip-hop music, as she is seen listening and singing along to it with a pair of headphones.
Lisa has a crush on a boy named David, who like Lisa herself, was born highly intelligent and enjoys studying science and other subjects. He also appears to be a male version of Lisa with one exception: Lisa likes biology as well as chemistry, while David does not.
According to Lori in "Garage Banned", Lisa removed Lincoln's appendix.
According to some information from The Loud House on Instagram:
She describes herself as "98% water."
She wants to travel to Alaska in the summertime for 24 hour daylight research.
No one has the clearance on her secrets.
Her biggest pet peeve is when a salad bar runs out of croutons.
She owes 50,000 dollars to the library for overdue books.
She is not skilled at arts and crafts, due to having stubby fingers.
She also speaks Mandarin, Latin, Swedish, and West Coast Rap.
She can make a time machine but not a PB&J sandwich. She also cannot zip up her sleep suit and has difficulty sleeping at night without a story.
She still takes naps. Her nap time does not coincide with Lily's as she is shown active while her roommate is taking her nap, and her nap time is at noon.
Despite being a genius, she's terrible at passwords, with her birthdate being the only password she goes by.
↑"Butterfly Effect" (in English). The Loud House. Season 1. Episode 11a. June 9, 2016. "Lisa: Flip's the only guy who will hire four-year-olds with no experience.; Katherine Mulligan: One has to wonder, where did it all go wrong for these girls? And why is a four-year-old working at a gas station?"
↑In "April Fools Rules", her parents address her name as Lisa Marie Loud. However, according to the "Ask Lincoln" segment in Instagram, their parents calls everyone "Marie" as a second name when they are in trouble.