Lil is a twin of Phil, Phil and Lil got along at a step at a time to get Dil to walk.
Lil and her brother Phil are twins who are alike in almost every way possible. Usually dressed to match, they both wear pink shirts with black pinstripes and turquoise outfits (Phil wears a shirt and Lil wears a dress) with a handkerchief on the left side and a duck on the right, and both have a small amount of brown hair on top of their oddly-shaped heads. Lil wears pink shoes, a pink bow on her hair and no shorts (exposing her diaper similar to Tommy Pickles) and is always drawn with ear lobes.
Lil is revealed to be older than Phil by two minutes. Lil and Phil also share the same interests: consuming worms (which they have often called "Chocolate Spaghetti") and toilet water. Lil finds grape drink and ketchup at the movies. They often use their "full/nicknames" names, Phillip and Lillian, against one another when arguing or simply speaking with each other or upsetting Tommy Pickles. Their parents, Betty and Howard, often confuse the two despite permanent differences, like the ears, as well as their genders and Lil's bow. It is often believed in various fan circles that the inspiration for their names may have come from Ayn Rand's book Atlas Shrugged, which features two in-law characters named Phillip Hardride and Lillian Rearden.
Lil is an adorable and tomboyishly beautiful female toddler and has peach skin and a pair of white eyes with small black pupils. She wears a pink shirt with black pinstripes, a turquoise dress with a white handkerchief on the left side and a yellow duck on the right, white ankle-length socks and pink shoes. The character has a small amount of brown hair usually combed down. She does not wear shorts, pants, or any type of clothing under her dress, exposing a white diaper.
Lil appears in most episodes of both the Rugrats TV series and the All Grown Up! show. Her first appearance in Rugrats was in Tommy Pickles and the Great White Thing, the pilot episode for Rugrats. Her last appearance in Rugrats was in Kimi Takes The Cake.
- Lil (along with Phil, Tommy, and Chuckie) discovered worms in "Moose Country", but in a later episode, "Moving Away", a flashback is shown from before the babies met each other, featuring Phil and Lil stating that they ate worms at the park.
- Eventhough Phil has the record on having the most camera views from inside his mouth. Lil, like Susie, only had hers once in the episode Together at Last.
- Although there was no episode, Lil was seen as a 2 year old in All Grown Up
- Lil wants to play with grape soda and ketchup dispensers at the cinemas.