During one point of the game, some reversed speech can be heard. When played backwards it says:

"There's something I have to tell you: The Walrus is Paul."

This is a reference to The Beatles song "Glass Onion", which features the line:

"I told you about the Walrus and me man, you know we as close as can be man, well here's another clue for you all: The walrus was Paul."

Spoiler:Another possible connection between the song and the game is the fact that the line "The walrus was Paul" is seen by conspiracy theorists as a message that proves Paul McCartney actually died in 1966 and was secretly replaced by a look-alike (as walruses apparently symbolize death in some cultures). Because Bad Milk's story is an interpretation of reincarnation, this could be the reason the developer's chose to use that particular line.
Contributed by Boyobmas