James Roday, the director for Treehouse, starred as psychic detective Shawn Spencer in Psych. A signature in the show was to feature a pineapple in every episode for fans to find. At the end of Treehouse, Peter's daughter is seen wearing a shirt with pineapples on it.
Peter makes several pop culture references throughout the movie including Silence of the Lambs, The Breakfast Club, The Witch, Ted Bundy, Rusted Root, Alice in Wonderland, Lord of the Rings, State Farm commercials, the humble brag, Akira, Hulu specials, and Charles Manson.
Julianna Guill, Jimmi Simpson, Michael Weston, and Sutton Foster all had guest spots on the television series Psych, which starred James Roday, the director of Treehouse.
Michael Weston (Lonnie) and Jimmi Simpson (Peter) starred together in another horror movie directed by James Roday, "Gravy".