The poem Mike Milligan (Bokeem Woodbine) recites is called "Jabberwocky" and is taken from the novel "Through the Looking-Glass and What Alice Found There" written by Lewis Carroll in 1872.
The song playing during the credits is a different version of "I Am a Man of Constant Sorrow", a song made popular in the Coen Brothers (Joel Coen & Ethan Coen) film O Brother, Where Art Thou? (2000).
Ed Blumquist (Jesse Plemons) tells Lou Solverson (Patrick Wilson) the story of Sisyphus, a Greek mythological figure condemned to push a boulder up a hill for eternity. This is not the first time the story of Sisyphus is referenced. Previously, in The Myth of Sisyphus (2015), Noreen, (Em Haine) can be seen reading the book of the same name by Albert Camus. Camus uses the story of Sisyphus in his book to explain the absurdity of life.
Karl's (Nick Offerman) attempt to barricade the door with a bench could be a reference to The Dude doing the same thing in The Big Lebowski (1998). In both cases the barricade is on the wrong side of the door.