At 2-years-old (15-months-old before Season 5), Lily is the youngest of the Loud siblings. She is able to walk independently, and is learning to speak. Before Lily was potty trained, she had a tendency of pooping in her diapers, leaving a foul stench known to disgust her older siblings, and often removed her diaper, forcing her siblings to constantly have to put it back on. Lily has a habit of crying. Lincoln always changed Lily's diaper in Lisa and Lily's room. Starting in "Schooled!", Lily attends Baby Bunker Preschool.
Lily is always happy, and enjoys being with her siblings. She does not cry too often, and didn't even cry much when she was a baby, though she did occasionally cry for no apparent reason, such as in "The Crying Dame". She is also the most well-behaved of the siblings, as shown in episodes such as "Suite and Sour" where most of the siblings misbehave but not Lily. Despite this, she is still known to misbehave on occasion, for example her various exploits that Lola recorded in "A Star is Scorned".
Even though she is just a toddler, Lily is shown to be fairly aware of her surroundings, and especially of her siblings' many antics, in which she is often swept up. In "Undie Pressure", she intentionally sucks on her pacifier to stop herself from crying, and ends up winning the challenge for her family. She becomes angry at Lincoln for posting their sisters' embarrassing moments online in "Making the Case", despite the fact that she was not even filmed; and she helps her sisters Lola, Lucy, Lori, and Leni convince Lincoln to choose Aloha Beach as their vacation spot in "In Tents Debate". In "Picture Perfect", along with her sisters she gets annoyed with Lincoln over him changing their behavior for his "perfect" picture. In "Ties That Bind" she is worried like the rest of her siblings about being kicked out, and gets upset with Lincoln when he says out loud how "he's always wondered what it would be like to be an only child". In "Along Came a Sister", she, along with her siblings wants to prevent Frances from getting killed. In "Come Sale Away", she gives a blank stare into the camera when the others continue to try and compete with each other to find her blanket.
Although still learning to talk, she seems to understand her brother and sisters quite often, such as when Luan wanted her to be a ventriloquist dummy. She is very cheerful, and loves to be near her siblings. She is most frequently seen in the care of Lincoln, Luna, Leni, and Lori.
It is implied that she is just as feminine as Lori, Leni, and Lola, as she wished to go to the beach, while Lincoln's tomboyish sisters wanted to go to an amusement park instead.
Despite her cheerfulness, she is not above fighting back if rubbed the wrong way. In "Brawl in the Family", she chastises Lincoln for continuing to butt into Lori and Leni's feud and later gets in a big fight with her sisters after Lincoln reveals things some of the sisters said about each other. In "Room with a Feud", after Lori accidentally steps on her phone, she retaliates by posting a humiliating photo of Lori online. In "Selfie Improvement", she gets angry at Lori for refusing to change her and removes her diaper, throwing it at Lori's face.
Despite being the youngest sibling (at only two years old), Lily is shown to be quite strategic, and a master at planning, similar to Lincoln. This is proven in "Any Given Sundae", where she intentionally sets off her sibling's antics to make sure she gets ice cream. It's once again proven in "Schooled!" where she wrecks her parents' attempts to potty train her, by setting as many traps to ruin their plan. In "Silence of the Luans", she sets off a bunch of disastrous pranks around the house, just to end Luan's retirement from pranks, showing her love of Luan's pranks.
"Lily Loud may be the smallest member of the Loud House, but what she lacks in size, she makes up for with her stinky surprises. She's a professional diaper ditcher, and loves drooling on everything. Even though she's known as The Poop Machine, Lily is everyone's favorite little buddy!"
As the youngest of the Loud siblings, Lily is very small, and usually just wore a white diaper in the first four seasons. She has one prominent tooth, and three strands of blonde hair on her head. As of season 4, she is now portrayed full-time with eyebrows, but in earlier seasons, she only had them when emoting with her eyes.
On occasions where she wore clothes in the first four seasons, she wore mainly lavender, the color associated with her (with some exceptions, such as the iPhone-exclusive game, Outta Control, where Lily's associated color is white). In "Linc or Swim", her swimwear is a lavender onesie with a picture of a strawberry on it, in the same episode, she wears a blue swim diaper with yellow ducks on it. Her nightwear consists of lavender footie pajamas. Her winter clothes is a lavender parka, with purple shoes, and gloves.
Starting in Season 5, Lily now wears a white T-shirt, lavender shorts, and white booties, and her strands of blonde hair appear to be thicker than in previous seasons. Plus, her eyelashes also appear to be longer and thinner than before.
Early in development, Lily had a tall poofy tuft of hair on her head. Later on, however, that tuft of hair was made shorter. This early design would later be the basis for Billy.
In earlier seasons, Lily wore a diaper to cover her lower area. She often defecated in it, causing one of her siblings or parents to change her into a fresh one. She would often take it off and run around naked, as her title as a professional diaper ditcher indicated.
Lily has a small lavender blanket, with purple frills on the edges. So far, it has had two major roles in the series:
In "Changing the Baby", Lincoln tried to implement his interests into Lily, since none of the other sisters had the same interests as him. When Lincoln believes Lily has changed, he tosses the blanket away, claiming she doesn't need it anymore. Later, when the siblings were trying to win Lily over with their own interests, Clyde, thinking Lincoln is replacing him with Lily, tries to win back Lincoln, by dressing up as a baby himself. Lily notices that Clyde is clutching her blanket, so she crawls over to Clyde to get it back. Seeing Lily do this makes Lincoln realize that the blanket is her own interest, and decides it's best not to change Lily, due to her attachment to the blanket.
In "Come Sale Away", the siblings got into a contest to see who could sell the most stuff during their garage sale. However, when they manage to sell all their stuff, Lily begins to cry. Lincoln notices that she needs her blanket to calm down, but when he and the other sisters can't find it, they assume that they accidentally sold it during their garage sale. When Lincoln and the sisters try to find the blanket, they notice that Flip appears to have it. However, when they all arrive back home, they realize that the blankets they got were actually rags that Flip gave them just to con them out of their money. As the siblings began to complain, it is shown that the blanket was at the house all along, as Rita was just washing it.
In a world where Lincoln has ten brothers instead of sisters, Lily is a baby boy named Leon.
Much like his female counterpart, his hair is light blond and he usually wears only a diaper. However, unlike Lily, Leon has two shorter, slightly thicker, strands of hair instead of three, and he has one extra front tooth. He also does not have any eyelashes like his female counterpart. In the dimension where Lincoln is the middle child of eleven sons, Leon is shown to be rather mean to Lincoln as shown when Leon bit Lincoln's finger when Lincoln just wanted comfort, much like the rest of their brothers But in the dimension with Linka, Leon is shown to be caring towards his sister. Much like how Lincoln tends to have a fatherly attitude towards his youngest sister, it can be assumed that Linka has a very motherly attitude towards her youngest brother.
Like all of his male siblings, Leon eventually ceases to exist, when it is revealed Lincoln's whole adventure was just a dream.
Lily's superhero form is the Deuce. The name comes from how a 2 playing card is referred to as a deuce and the phrase "dropping a deuce", meaning to poop.
The Deuce wears a red mask with a white card that has a "2" on it, red gloves, and a yellow bib, plus Lily's usual diaper.
In "Pulp Friction", she fights off Wild Card Willy's goons with her dirty diapers in the comic Lincoln created.
The gas monster that appeared in the "Deuces Wild" comic and short might be an alternate version of Lily, seeing as how Ace Savvy, One-Eyed Jack, and the Full Deck (without The Deuce) fighting against the gas monster was actually Lincoln, Clyde, and Lincoln’s sisters changing Lily’s diaper. However, it is also possible that the gas monster represents the soiled diaper and/or the smell of it, rather than Lily herself.
Despite having one tooth, Lily does have a full set of teeth when she is grinning or scared.
While not as intelligent as her sister, Lisa, Lily seems rather intelligent despite being only two years old (fifteen months old prior to Season 5), as she seems to have a pretty good understanding of what is going on around her.
Lily is left-handed.
Based on her appearance during "Luan Loud's April Fool's Highlight Reel" in "April Fools Rules", she could've been born sometime during January, February or March as the video was of the preceding April Fool's Day.
Lily's hair looks similar to the cowlick on Lincoln's hair.
Luan, Lincoln, and Lisa all occasionally showed the ability to translate Lily's babbling in the first four seasons. However, this was not completely reliable, as in "Any Given Sundae", they couldn't understand her when she tried to tell them to behave so they could go out for ice cream later.
At times, Lily displays a natural talent for photography, as shown in "Out of the Picture", when she provided Lola with a better school photo for the latter's yearbook, and in "Room with a Feud", when she took a grotesque picture of Lori before spitefully posting it online.
In "Out of the Picture", "Room with a Feud", and "Anti-Social", Lily was shown to have a pretty high knowledge of how to use technology, as she is seen using a tablet in the former episode, and a cell phone in the latter episodes.
In the episode "L is for Love", it shows that Lily has a romantic infatuation with her teddy bear, and that she has a talent for drawing, when she drew a picture of herself, and the teddy bear she had a crush on.
According to Lynn's Q&A, Lily beat her in a thumb war.
According to episode 20 of the Nick Animation Podcast, Lily wants to watch a movie but her family doesn't let her.
According to some information on the Loud House Instagram:
The one place in the world where she would want to go to is mama.
Her biggest pet peeve is "boo-boo", which either means something scary, or an injury.
In "Any Given Sundae", she can use her diaper to mop the floor. This episode also reveals that she can read numbers, although the game Welcome to the Loud House implies that she likely cannot read words, judging by the fact that when handed Lucy's book of poems, she does not even try to read it.
She also voices their male counterparts from the episode "One of the Boys".
Prior to Season 5, Lily sometimes has trouble pronouncing the letter "L", as shown when she calls Lincoln "Incoln" in several episodes and "Yincoln Youd" in "White Hare", Lisa "Sa-sa" in "Friend or Faux?", Clyde "Cad" in "Game Boys", and herself "Wiwy" in "Write and Wrong". However, there are some times when she pronounces her "L"s correctly, such as in "Tripped!" when she pronounces the L's in Vanzilla's name correctly, and in "A Star is Scorned" when she correctly pronounces her own name, Lola's name, and the word "love". As of Season 5, she pronounces her "L"s correctly more consistently, even pronouncing Lincoln's name correctly in "Season's Cheatings".
It is unknown when her nap time is, but in Living Loud: Lincoln's List, Lisa is shown awake while Lily is napping, and in "House of Lies", it is revealed that Lisa's nap time is at noon. From this, it can be concluded that Lily's nap time is not at noon.
Until "Silence of the Luans", Lily was the only Loud besides Luan who has gone through an April Fools' episode without being pranked, that being "Fool Me Twice". She is pranked by Luan with blue paint alongside the rest of the family in "April Fools Rules", is pranked by Luan replacing her with a monkey in "Fool's Paradise", and gets drenched with onion water by Luan in "Silence of the Luans". In the latter episode, not counting flashbacks, Lori also did not get pranked due to being away in college.
As of 2021, Lily is the only Loud sibling who hasn't made her own Listen Out Loud podcast due to being a toddler.
Lily's first word she said in the series besides "Poo-poo" was "Blankie", which was said in "Changing the Baby". The first sentence she said in the series was "You Yincoln Youd" (an attempt to say, "You're Lincoln Loud") in "White Hare".
During season 5, Lily says "Poo-poo" less frequently and starts talking more (though she still says it in the theme song).
In the same episode it was revealed that Lily was the one who was pranking the Loud family, this led to Luan gaining inspiration from her younger sister to continue her pranking on April Fools' Day after she retired in the beginning after the events of "Fool Me Twice".
"The Sweet Spot" reveals that Lily throws things in Vanzilla, and as such, Lincoln doesn't like to sit next to her carseat.