The Way Of All Flesh (1903) is a book by Samuel Butler.

The Cradle to Grave is a common phrase, the usage ranges from songs, movies, books to metal bands to name a few.

I Live Again : Caleb rises from the grave spouting ‘I live again’ which is directly taken from Army Of Darkness (1992), when Ash's evil counterpart resurrects.

The Grave of Eric Draven : Just after leaving the mausoleum, turn right: You can see a hedge around the corner. The rightmost part of it is coloured differently than the the leftmost, open it and you'll find the grave of Eric Draven, from the movie The Crow (1994).

Nevermore : Upon pressing the grave of Draven, Caleb says the famous line from Edgar Allen Poe’s The Raven (1845), ‘nevermore’. Coincidentally Eric Draven quotes Poe a few times as well.

Morningside Cemetery : The main building found in the level is named after the cemetery in the movie Phantasm (1979).

The Sink : “Out, out damned spots!” (originally “Out, damned spot! out, I say!”) is a line from Shakespeare’s MacBeth which Caleb says upon using the sink in the crematorium.

The wrong side of the tracks is an old saying referring to bad luck; The side wrong side of the tracks is where the smoke from engines falls to.

Zombies : After blowing up the outside of a trainwagon, Caleb comes across barrels containing zombies, that are taken from Return of the Living Dead (1985) and says “Fresh victims for the ever growing army of the undead” which is a line said by members of the Army of Darkness (1992) from the movie with the same name.

Miskatonic Station : Caleb makes his way to the Miskatonic Station which is a reference to Miskatonic University, a university in a place called Arkham invented by horror fiction writer Howard Phillips Lovecraft in the Cthulhu Mythos books.

Innocents : This is the first level where you encounter the Innocents. They don't have much in the way of obstructing your way, rather they all just want to go home. Their line “There's no place like home” is a direct quote from the movie The Wizard of Oz (1939).

Get off my train : ‘Get off my train!’ is a line expressed by the subway ghost in the movie Ghost (1990).

Kimble : You can find Richard Kimble’s prison suit from the movie The Fugitive (1993) behind one of the crashed trainwagons.

Duke Nukem : Behind the performance room of JoJo, you will find a mangled up Duke Nukem. When entering the room and pressing on Duke, Caleb says the famous lines used by Duke Nukem: “I got time to play with you” (originally Duke says “I don't have time to play with myself”) and “Shake it baby”. Both from the game Duke Nukem 3D (1996).

Ophelia : At the top on the altar, you will find Caleb's dead wife Ophelia. Her name is taken from Shakespeare’s Hamlet (1602).