Lila is, as Helga puts it, "little miss perfect". She has a tendency to add the words "ever so" or "oh so" to just about every sentence she speaks, and she's very polite, sweet, and kind. This leads her to bond quite easily with Olga, as the two have similar interests. But in truth, Lila has a darker side to her. As she sings about in "Eugene, Eugene!", she is very sad on the inside and purposefully puts up her perfect persona to hide it. This essentially makes her the opposite of Helga, who puts up a mean persona to hide her kind self.
Lila is always seen wearing a green dress, combined with green shoes. Her hair has two pigtails with bows at each end. In her first few appearances, her hair was red, but in later episodes, her hair is brown. As of Hey Arnold! The Jungle Movie, she retains her appearance from the series, with the exceptions that her sleeves are puffier and her shoes are changed to brown cowgirl boots.
Lila makes her first appearance in the episode "Ms. Perfect". She is a new student at P.S. 118. She's new to "the big city," having moved with her father from Pleasantville, a farming community. She's as smart as Phoebe, as stylish as Rhonda, and the most popular girl among the boys. At first, the other girls are jealous, but when they learn about her humble, disadvantaged home life, they begin to sympathize with her.
Helga's dislike for Lila later resurfaces in the episode "Arnold & Lila", even though it is the result of Helga's own actions. Lila decides that she "like-likes" Arnold after finding "Arnold Loves Lila" written on an alley wall while walking home from school. Arnold initially rejects Lila's advances, but eventually develops a crush on her. But by that point, Lila has already gotten over her romantic feelings for Arnold, and says that while she's flattered that he has a crush on her, she only likes him as a friend.
In "School Play", she is assigned the penultimate understudy, making her the last person Helga has to get through in order to play Juliet opposite Arnold as Romeo. However, all of Helga's attempts to get Lila to quit fail. Lila suddenly begins to hint she knows why Helga wants to play Juliet, and says she would be willing to quit if Helga admitted she liked Arnold. Helga stubbornly admits to Lila that she does have a crush on Arnold, and Lila willingly gives the role to Helga. Some have speculated that Helga's crush on Arnold could be a reason why later on, Lila continuosly turns down Arnold's advances, and states she only likes him as a friend.
In "Timberly Loves Arnold", Timberly asks Arnold, "Did anyone ever really hurt your feelings?," and Arnold sadly looks at Lila. After Arnold gets turned down again by Lila at the end of the episode, this time for something Arnold did that even he finds indefensible, he finally decides to try to let go of his romantic feelings for her.
- In the episode "Weird Cousin", we learn she does not like scary movies.
- In the episode "Love and Cheese", we learn that Lila can't swim and that she's allergic to stuffed animals.
- In the episode "Eugene, Eugene!", she is shown to be a good, if plain, singer.
- It is also revealed that “Eugene, Eugene” (the fictional play featured in the episode) is her favorite musical.
- In the episodes "Love and Cheese" and "Timberly Loves Arnold", she gets sick on bigger rides.
- Her personality may be inspired by that of Becky Thatcher from “The Adventures of Tom Sawyer” by Mark Twain. Lila’s last name also may be a nod to the titular character.
- Despite her kindness and sweetness in just about every episode, in the episode "Phoebe's Little Problem", Lila makes a rude and bored face with the other kids while Phoebe is giving a speech. This is explained by Craig Bartlett in an online chat. He says, "The truth is, the writers didn't think about them, just the main story...and the artists may draw them looking bored, for example, and the fans are all 'hey, they don't even care about Phoebe!'"
- In an interview, Craig Bartlett claims that Lila has a repressed dark side and in another interview, he says that she seemed innocent at first and that the writers didn't hate her until she started seeming evil, although he says that he himself likes her and is apologetic about dragging out Arnold's pining for her too long.
- In an interview on The Arun Mehta Show, Craig Bartlett said that she would not make an appearance in Hey Arnold! The Jungle Movie". This later turned out to be false, as she appears in the scene on the Sunset Arms roof. It's possible that Bartlett simply meant that Lila would not be among the kids who go to San Lorenzo for the main plot of the movie.
- 30b. Ms. Perfect
- 48b. Helga vs. Big Patty (cameo)
- 49b. Hey Harold! (no lines)
- 50b. Gerald's Tonsils (no lines)
- 55a. Arnold & Lila
- 59. School Play
- 60. Parents Day (no lines)
- 62. Dinner for Four / Phoebe Skips
- 67a. Helga's Parrot
- 68a. Love and Cheese
- 69a. It Girl
- 72a. Back to School (cameo)
- 73a. Weird Cousin
- 74b. Fighting Families (no lines)
- 76b. Synchronized Swimming (no lines)
- 77a. Helga's Masquerade
- 81b. Big Sis
- 83b. Principal Simmons (no lines)
- 84b. Phoebe Breaks a Leg (no lines)
- 85b. Rhonda Goes Broke (cameo)
- 90. Arnold Visits Arnie / Chocolate Boy (no lines)
- 91a. Harold vs. Patty (cameo)
- 94a. Phoebe's Little Problem (no lines)
- 96. Married
- 97. Timberly Loves Arnold / Eugene, Eugene!
- Hey Arnold! The Movie (no lines)
- 98. April Fool's Day (no lines)
- Hey Arnold! The Jungle Movie (no lines)