You've got to start somewhere, and for many of the cast of "Stranger Things," their early credits included guest star roles on "Law & Order," "Law & Order: Special Victims Unit" and "Law & Order: Criminal Intent."
Since most of these guest star roles on these crime dramas are, of course, rapists, murderers, or other especially heinous perps, don't be shocked at who these familiar faces played. Sorry to tell you, both of Eleven's father figures played some very creepy guys.
Cara Buono, "Law & Order," "SVU," "CI" (1996- 2008)
Before playing Karen Wheeler, Buono had recurring roles on "Third Watch," "Mad Men," and "The Sopranos." She also was a frequent "Law & Order" guest star. In the 1996 episode "Girlfriends," she played a murderous co-ed running a call girl ring at collage with her rich Daddy. She returned in a radically different role in 1998 as a female prisoner against whom Abbie Carmichael (Angie Harmon) seems to have a personal vendetta. She also costarred in the 2008 "Unorthodox" episode "SVU" as the mother of a young male rape victim. And, she guest starred in a 2002 episode of "Criminal Intent" based on the real-life Jean-Claude Romand case.
Catherine Curtin, "Law & Order," "CI," (2000- 2008)
Besides playing Dustin Henderson's mom, Curtin has appeared on "Orange is the New Black," "Insecure," and "Homeland." And she also guest starred in the Season 6 episode of "Criminal Intent" as the acting coach of a murdered girl (whose mother was played by Liza Minnellli). She also guested on episodes of "Law & Order" in 2000 and 2008.
David Harbour, "SVU" (2002)
Harbour (aka Detective Hopper)'s first acting credit was as a waiter in a 1999 episode of "Law & Order." But he got to really emote in this "SVU" episode as a pedophile who was obsessed with kidnapping little girls and dressing them up like dolls. It all had to do with a very disturbing childhood and his late mother's doll collection, which he inherited. In the end, he does the right thing and confesses where his latest victim is so she can be safely returned to her mother (Gloria Reuben). He also guest-starred on two episodes of "Criminal Intent."
Matthew Modine "SVU" (2005)
Before he played manipulative Dr. Martin Brenner on the Netflix series, Modine Stabler guest starred as pedophile/murderer Gordon Rickett, who escaped prosecution once before. Now, in this episode that's almost entirely one long interrogation, Olivia Benson (Mariska Hargitay) takes a few rounds, but nailing this perp has become personal for Elliot Stabler (Christopher Meloni). Stabler's hunches pay off and they catch Rickett before he can kill his next victim.
Cary Elwes, "SVU" (2007)
Elwes was a long way from "The Princess Bride" (but not so far from his sleazy mayor on "Stranger Things" Season 3) as a mob lawyer who fears his daughter (Emily VanCamp) might have brutally murdered his wife while high. He blocks Stabler and Benson every step of the way, then is relieved when they prove his daughter is not the culprit.
Sean Astin, "Law & Order" (2008)
The "Lord of the Rings" alum (aka helpful, sweetly nerdy Bob Newby on "Stranger Things") guest starred as a radical Christian preacher who urged his young followers to wage holy war on non-believers. Including encouraging one boy to stone his "immoral" mother to death.
Caleb McLaughlin, "SVU" (2013)
Relax, Lucas Sinclair is not the "born psychopath" of this episode. (That's Ethan Cutkosky, who went on to play Carl on "Shameless." In this episode, the title character is Henry, a 10-year-old psychopath who terrorizes his sister, attacks his mother and -- gasp! -- drowns a dog.) McLaughlin is just a kid full of questions when Det. Amaro (Danny Pino) does a Q&A at an elementary school. In quick succession, he fires off: “Do you ever shoot anybody?” “Is your gun even real?” “Do you wear a bullet proof vest?” before Amaro is called to a crime scene.