It's not every day that a series can introduce a new major character partway into a successful run and have that character turn out to be one of the best in the whole show. Honestly, it's more or less unheard of. But Netflix's Stranger Things is pretty much known for defying expectations and breaking with conventions, so it's not at all a surprise that it managed to do all of that and more with the introduction of Lucas Sinclair's little sister, Erica.

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Despite only appearing in a handful of short scenes in Stranger Things 2, Erica quickly stole viewers' hearts and became something of a viral sensation. Actress Priah Ferguson was promoted to a series regular for Season Three, and all along the way, remained arguably the series' sassiest, and downright funniest character. Here are some of her most iconic lines.

"Nerd."

During the second season, Erica primarily exists to drag her brother whenever she can, absolutely roasting him in public and in private. During the season's Halloween episode, when their mother is taking photos of Lucas in his Ghostbusters costume, Erica is practically beside herself with humiliation.

"God, you are such a nerd," Erica observes while watching Lucas pose in his Venkman uniform. "No wonder you only hang out with boys." After being scolded by both her brother and mother for her attitude, Erica is momentarily silenced, but not even that can keep her from mouthing an accusatory "nerd" at her brother.

"You can't spell America without Erica."

During Stranger Things' third season, Dustin, Steve, and Robin find themselves on the brink of exposing a conspiracy right in their own backyard. They realize that they're in need of someone small who can crawl through air ducts unobstructed. Enter sass master Erica Sinclair.

Dustin tries to guilt Erica into taking part in the scheme - a scheme that Erica herself even cheekily refers to as Operation Child Endangerment. As part of his attempt, he essentially asks Erica if she's a patriot who loves her country - to which Erica offers the absolutely perfect reply, "you can't spell America without Erica." Dustin's dumbfounded reaction says it all.

"Code red? I got a code for you instead. It's called code shut your mouth."

Considering how little patience Erica has for her own brother, it makes perfect sense that his friends absolutely drive her batty, too. During the climactic episodes of Season Two, Erica finds herself annoyed by Dustin's frequent attempts at calling Lucas via walkie talkie, screaming about the newest code red in his experiences with Dart.

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Erica, playing with her dolls and Lucas's action figures at the time, is absolutely at her breaking point with Dustin and all of Lucas's foolishness. So rather than let Dustin continue screaming on end, she answers his call. "Could you please shut up?" she asks him point blank, before going on to absolutely destroy him: "Code red? I got a code for you instead. It's called code shut your mouth."

"Keep saying my name. See what happens."

As we've already explained, Erica really loves to drive her brother crazy, and she will take any opportunity she can to needle at him whenever and wherever possible. She also has basically no time for any of his friends, except for Dustin, as long as ice cream is involved. Once all the boys are reunited at Starcourt Mall toward the end of the third season, Erica is there to witness their sweet and sappy reunion.

If there are two things Erica is definitely not, it's sweet and sappy. After snarking at them to not cry in front of her, Erica is once again yelled at by Lucas, who just calls her out by her name. In response, she threatens Lucas, "keep saying my name. See what happens."

"Oh, I can fit. I just don't know if I want to."

Stranger Things Season 3 Trailer - Erica

Despite her diminutive stature and young age, Erica is nothing if not a shrewd little businesswoman. After she listens to Dustin, Steve, and Robin's plans for her to crawl through the air ducts in the Starcourt Mall, she makes it perfectly clear that she's got her own goals in mind as a result of this deal.

So, when she's questioned about whether she doubts that she'll be able to fit into the ducts, she quickly shuts that notion down: "Oh, I can fit. I just don't know if I want to."

"You're all so nerdy, it makes me physically ill."

Dustin Robin Erica and Steve in Stranger Things Season 3

If there's one thing Erica Sinclair can't stand, it's nerdiness. At least, she likes to act like that's the case. As the third season reveals, Erica may be a bit of a nerd herself, regardless of whether she's willing to admit it. During the season, Erica finds herself trapped in the bowels of the Starcourt Mall with three of the show's biggest nerds of them all: Dustin Henderson, Steve Harrington, and self-proclaimed band geek Robin.

Erica is brought along on their nerd journey into the secrets of Starcourt's Russian lab, even if she didn't exactly agree to that. Along the way, she witnesses all of their bickering and plans and discussions of aspects of nerd culture, eventually causing her to snark, "you're all so nerdy, it makes me physically ill."

"Free. Ice. Cream. For. Life!"

Erica Sinclair with ice cream in Stranger Things 3

In exchange for her services as the vent-crawling spy in the Scoops Troop's plan, Erica has a simple request: she wants free ice cream from Scoops Ahoy, whenever she asks for it.

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Somehow, this plan is agreed to by all parties involved, so after Erica makes it through the vents and all the way to the destination, she opens the locked doors and reminds Steve, Robin, and Dustin of her request: "free. Ice. Cream. For. Life!" But with Starcourt Mall now being destroyed, we're not sure how Erica will collect on that deal.

"Um, I'm ten, you bald b*****d."

Erica yelling as Dustin watches in Stranger Things

Once all the characters have reunited in Starcourt Mall and begin to plan their next attempt at attacking the Russian lab, resident theorist Murray Bauman suggests a plan of attack that Erica has no problem absolutely tearing to shreds.

After having all the problems with this suggested plan of action pointed out to him by a litte girl, Murray is flummoxed, frankly asking, "I'm sorry, why is this four year old speaking to me?" Erica, of course, has no time for this patronizing remark, and immediately fires back, "Um, I'm ten, you bald b*****d."

"Just the facts!"

Erica Sinclair in Stranger Things Season 2

One of the only lines Erica has uttered on multiple occasions, and that could therefore serve as her own snarky little catchphrase, is "just the facts!" Whenever Erica is called out for her attitude and general rude behavior, she's quick to point out that she's not really being rude - she's just telling the truth.

The first time she says "just the facts!" is when her mother scolds her for mocking Lucas's nerdy behavior. She says it again when she's yelling at Murray about the idiocy of his plan of action in the third season finale. Erica might be small, but she's one of the smartest players in this whole game. It's about time people wake up and accept the facts for what they are.

"Isn't it past your bedtime?" "Isn't it time you die?"

Erica Sinclair insulting Lucas in Stranger Things 3

The playful rivalry between Erica and her big brother Lucas has been a big part of both of their arcs since Erica was introduced in the second season. But the full extent of their adolescent attitude was finally revealed early on in the third season premiere.

When he sees Erica and a group of her friends sitting around eating ice cream, Lucas yells, "isn't it past your bedtime?" Erica quickly yells back, "isn't it time you die?" A war of insults follows, but it's clear that Erica won this war long before it ever even started.

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