Prior to that appearance, KJ had only addressed Perry's death publicly with some simple Instagram posts.
One was a reference to the Third Eye Blind song The Background, which includes lyrics like: "Everything is quiet since you're not around, and I live in the numbness now, in the background."
The other was his favourite photo of Luke Perry with the message "Rest in love bro".
KJ told Fallon he chose the particular photo of Perry because, "I just think he's in complete and utter peace in that photo".
Earlier this week, Luke's final scenes as Fred in 'Riverdale' were aired, in which he was seen comforting his son after he was accused of committing a crime. As of the time of writing, it's not known how the show's writers will tie up Fred's storyline in the wake of Luke's passing.
Meanwhile, fellow 'Riverdale' star Mark Consuelos recently hailed Luke as "one of the good ones".
He said: "All the great things you've heard about Luke? They're all true. That's who he was. He was an amazingly generous, kind person. You can't fake that. He was one of the good ones."
-Bang! Showbiz