Garry Marshall, the creator of the original series (The Odd Couple (1970)), who served as consultant on this version and plays Oscar's dad, died on July 19, 2016. On the wall in Oscar's apartment is a photo of Oscar (Matthew Perry), Felix (Thomas Lennon), and dad Garry as tribute to him.
Lauren Graham plays Oscar's ex-wife Gaby. Matthew Perry and Lauren Graham are very good friends and dated briefly in the past. She also appeared in Go On (2012), in which Matthew Perry also starred. Graham also had a guest spot on "Studio 60 on the Sunset Strip" in which Perry's character asks her out and she accepts--albeit unwillingly.
Matthew Perry and Thomas Lennon previously starred together as mismatched best friends in 17 Again (2009).
Oscar's (Matthew Perry) first line to a radio caller in The Odd Couple (2015) is the same first line from the premiere of Go On (2012), in which he also starred.
Thomas Lennon guest-starred on the "Friends" episode "The One in Vegas: Part 1 (1999)" as Randall, Joey's hand twin.