In 1984, she spent the months of October and November tormenting her brother, making fun of his Ghostbusters costume, touching his radio and action figures without his permission, and teasing his crush on Max Mayfield.
In the summer of 1985, following the town's Starcourt Mall opening, Erica would spend her days with her posse of friends harassing Robin Buckley and Steve Harrington for free ice cream samples at the mall's ice cream parlor, Scoops Ahoy. She is soon asked by Steve, Robin, and Lucas' best friend Dustin Henderson to climb through the mall's vents to investigate the mall's supplies that withhold Russian weapons. Erica agrees in exchange from free ice cream for life. This simple task proves to be anything but, as the quartet discover a large Russian base underneath the mall attempting to open a portal to another dimension, a portal she discovers her brother and friends have battled to keep closed for the last two years. While assisting Dustin, she soon discovers that she holds nerd-like qualities with her love of My Little Pony, politics, and skills in math. Though Erica is initially in denial, Dustin tells her to embrace her nerdy nature. After escaping the base, she soon assists her brother and friends stopping the Mind Flayer. Three months later, Erica is given Dungeons & Dragons sets by Dustin and Lucas.
Erica is the somewhat typical "annoying little sister" to Lucas and a source of irritation to him. She constantly calls him weird and annoying due to his nerdiness and for the same reason isn't fond of Lucas' friends, thus barely showing any respect to them. She has her own set of friends that she hangs out with, particularly abusing the sample privileges of Scoop's Ahoy, an ice cream shop in Starcourt Mall. However, despite her abject disapproval of nerds, Dustin points out her gift for mathematics, her knowledge of politics and her interest in My Little Pony made her just as nerdy as he was. It's also implied she sneaks into his room and steals his stuff, such as Lucas' He-Man action figure. Erica is very politically knowledgeable for her age, and has a patriotic attitude toward her country.
Additionally, while she does not doubt the existence of the Upside Down and the creatures that come from it after Dustin explains them to her, she initially refused to believe that Lucas was involved with either of them until he helped save her from the Russians. She is also incredibly self-centered, choosing to help Dustin, Steve and Robin infiltrate the Russian base beneath Starcourt Mall due to the promise of free ice cream, rather than a genuinely altruistic spirit. In the end, however, she softens up to the gang and the boys give Erica their Dungeons and Dragons set.
Erica would taunt her older brother Lucas and annoy him, becoming a source of irritation for him. In 1985, when Erica learned about Lucas and his friends' encounters with the Upside Down and its monsters, she did not believe that Lucas was involved in any of it despite believing everything that happened. That changed, however, when Lucas came to her rescue at Starcourt Mall. Though Erica still annoyed Lucas, the two worked together in defeating the Mind Flayer and closing the Gate. Three months later, Erica was given all of her brother's and friends' D&D set which she accepted; hinting the two would grow a better relationship with each other and that Erica would accept her nerdiness.
Erica was very dismissal to her older brother's friends, including Dustin Henderson. When Dustin tried to get in touch with Lucas to inform him about D'Artagnan, Erica did not bother to help Dustin and turned off Lucas's Supercom.
However, in 1985, they soon formed a friendship when Dustin requested Erica's help in discovering a secret Russian base underneath Starcourt Mall. Erica did not bother believing Dustin about Upside Down and its monsters, despite not believing her brother to have witnessed all of it. When Dustin found out Erica was a nerd, Dustin would playfully call her a nerd, much to her annoyance as he slowly convinced her to accept it. The two worked together in rescuing Steve and Robin from the Russians and then protecting and caring for them after they were drugged with truth serum. Erica did not believe the existence of Dustin's girlfriend, Suzie until he confirmed her existence by contacting on Cerebro. As Dustin and Suzie sang Neverending Story, Erica was shocked and out of annoyance, ended their transmission after Suzie gave out Planck's constant and the two started expressing their love for each other. Three months later, Erica is shown to still be on friendlier terms with Dustin as she was given the Party's D&D sets.
After the opening of Starcourt Mall, Erica became a frequent customer at Scoops Ahoy where she kept asking for samples of different flavors of ice cream, much to the annoyance of Scoops Ahoy employee, Robin Buckley. When Dustin couldn't fit into the air vents to get to the secret room at the mall guarded by the Russians, Erica was asked by Robin to help them as she was small enough to fit through the vents. Erica, agreed to help, on the condition that she gets free ice cream for life, which Robin accepted. As Erica climbed through the vent, Robin guided Erica to the secret room and seemed relieved when Erica made it out of the vent and entered the room safe and sound. When trapped in the secret Russian base underneath Starcourt, Robin helped Erica and Dustin escape when they were spotted by Russians, leaving Robin and Steve to be captured. However, Erica and Dustin managed to come to Robin and Steve's rescue and escape the base together, as they protecting the older teens as they were drugged with truth serum until they were cured. Both Robin and Erica continued to work together in helping stop the Mind Flayer.
After the opening of Starcourt Mall, Erica became a frequent customer at Scoops Ahoy where she kept asking for samples of different flavors of ice cream. It's possible she irritated Steve for taking advantage of Scoops Ahoy's free ice cream samples, much like she did with Robin. However, when Robin asked for Erica's help to crawl through the air ducts to a secret room that the Russians occupied, Steve agreed to the idea and was willing to give Erica free ice cream treats, in exchange for her cooperation. Once Erica arrived to the room safe and sound, Steve gave out a sigh of relief. However, after becoming trapped in the room which turned out to be an elevator, Erica started to blame Steve and the others for putting her this situation, only to be taken aback when Steve snaps at her, saying that he doesn't care and they would be dead if they remain trapped in the elevator, much to Erica's shock. When exploring he secret Russian base underneath Starcourt, Steve helped Erica and Dustin escape when they were spotted by Russians, leaving him and Robin to be captured. However, Erica and Dustin managed to come to their rescue and escape the base together, protecting the older teens as they were drugged with truth serum until they were cured. Both Steve and Erica continued to work together in helping to stop the Mind Flayer.
Erica is the second youngest sister of a member of the Party, after Holly Wheeler. Erica has learnt about the Upside Down and its inhabitants while Holly noticed them, but was ignored.
Despite her brother Lucas' prominence, the existence of Erica was never hinted at throughout the first season, while the other Party's siblings were involved or introduced throughout the plot.
Erica was the second person of color to join the main cast, after Lucas, and would be followed by Argyle in the fourth season.
Her nerdiness is displayed through her love of politics (specifically her favoritism towards Capitalism and her hatred for Communism), her talent in mathematics, and her knowledge of My Little Pony lore. Her nerdish side is enhanced in the fourth season when temporarily joining the Hellfire Club for Dungeons & Dragons.
Erica is the second character in the series debuting as a recurring character before returning as a main character, behind Steve Harrington, and would soon be followed by Murray Bauman.