Reiser will play Dr. Owens, a high-ranking member within the Department of Energy on a “cleanup” assignment, tasked with containing the events of last year.
Astin is Bob Newby, a kind-hearted former nerd who went to high school with Joyce (Winona Ryder) and Sheriff Hopper (David Harbour) and now manages the local Hawkins RadioShack.
Berthelsen will portray Roman, an emotionally damaged, magnetic young woman who suffered a great loss as a child. Although she does not live in Hawkins, she mysteriously is connected to the supernatural events at the lab.
In addition to Ryder and Harbour, they’ll join new series regulars Sadie Sink and Dacre Montgomery, along with Joe Keery, Noah Schnapp, Finn Wolfhard, Gaten Matarazzo, Caleb McLaughlin and Millie Bobby Brown.
Mad About You alum Reiser stars on Amazon’s period comedy Red Oaks. He also created and will executive produce There’s Johnny!, set to stream on Seeso in 2017. Astin, known for his roles in the Lord of the Rings trilogy and The Goonies, stars in the feature Unleashed and recently joined the voice cast of Minecraft: Story Mode. Danish actress Berthelsen has appeared in Danish TV shows Exitium and The Desert.