Before “Stranger Things,” Netflix’s breakout summer hit, Joe Keery had never traveled for work. “I was pretty nervous,” the 24-year-old actor, recent DePaul graduate and Chicago resident told the Journal. “We did a table read [in Atlanta] and Winona Ryder was there; I was freaking out.”

Keery, who plays Nancy Wheeler's (Natalia Dyer) high-school jock boyfriend Steve Harrington, is part of an ensemble cast that includes largely unknown actors fighting off the threat of a supernatural takeover of the small town of Hawkins,...