Preferring to do one of those "walk around the studio" monologues, the Stranger Things actor eventually found himself in the lair of the Demogorgon, brushing shoulders with the likes of Kate McKinnon, Aidy Bryant, Beck Bennett, Pete Davidson, Kenan Thompson, and even SNL creator/producer Lorne Michaels. When Davidson broached the subject of Hopper's death at the end of Stranger Things' third season, Harbour dodged a spoiler-y conversation by saying, "Just watch the show, you'll find out next season."
In addition, he made light of the fact that a good chunk of his Stranger co-stars "are all going through puberty at exactly the same time, so set is a blast."
Later in the evening, a pre-filmed parody of Todd Phillips' Joker was shown—an inspired sketch that substituted Gotham's Clown Prince of Crime with Oscar the Grouch. In this dark and seedy origin story for the rancorous Sesame Street character (aptly titled "Grouch"), Harbour plays a garbage man who slowly loses his mind and ends up living in a metal trash can. "R-rated" versions of Bird Bird, Bert and Ernie, and Elmo also show up in the segment.
Since Joker filmed many of its scenes in the Bronx, SNL was able to travel to shoot at those places, too, including the soon-to-be-iconic flight of stairs where Arthur Fleck (Joaquin Phoenix) does his little dance before appearing on Murray Franklin's talk show.
Following his take as Anung Un Rama in Lionsgate's ill-fated Hellboy reboot earlier this year, Harbour's next big screen appearance will be as Alexei Shostakov (aka Red Guardian) in Marvel Studios' Black Widow standalone movie in May of 2020.