Erica Sinclair, portrayed by Priah Ferguson, is a main character in Stranger Things, being introduced in the second season as a recurring role before being promoted to the main cast from the third season onward. She is the younger sister of Lucas Sinclair.
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.
In the spring of 1986, Erica's skills at Dungeons & Dragons rival those of the Hawkins High teens. When Lucas's basketball games interfere with Hellfire Club, Mike and Dustin are desperate to find a substitute player — and Erica may just be the dark horse they need. Later, she is informed of an entity called Vecna murdering teens around Hawkins where she joined her friends and brother in attempting to murder Vecna. After a brief scuffle with members of the Hawkins High basketball team at the old Creel House, Erica and her friends were able to fend off Vecna, but were unable to prevent four gates to the Upside Down being opened. In the aftermath, Erica and Lucas visit Max Mayfield in the hospital as she placed in a coma, following their encounter with Vecna before witnessing particles from the Upside Down falling down into the town of Hawkins.
