When the narrator says "I met a guy once, he was a boy I guess, he might've had a name, started with an H I think." This is a reference to Harmony Korine, the writer/director of Gummo.
Bunny Boy is writer/director Travis Darkow's love letter to cult classic film, Gummo.
The film follows an older version of Bunny Boy from the film Gummo, as well as older versions of some other characters as well. The cowboy kids are featured, and the narrator is an adult version of Solomon. You see Tummler and Solomon's name written on wood near Bunny Boys tree-house at the beginning of the film, and when the narrator mentions "a guy that used to be a legend around here" towards the end of the film, this is a reference to Tummler as well.
Gummo, the film that Bunny Boy is based on, was set in the town of Xenia, Ohio. In real life, Xenia was destroyed by a tornado in 1974, Gummo references this disaster, and shows the town in the present, which was 1997 at the time, the same year the film came out, and shows how the town never fully recovered. Bunny Boy takes place 22 years after Gummo, and features grown up versions of Bunny Boy, the cowboy kids, and Solomon as the narrator
The tree-house that Bunny Boy lives in is located in Guillemot Cove in Washington, and is called the Stump House. The note that Bunny Boy pulls out of the tree and reads was a note that was found at the location on the day of shooting, and was incorporated into the film.