The quote is taken from a song by the Beatles (obviously) called I am the walrus.
Metrolyrics provides the lyrics, and I will just quote the first part (the rest does not make more sense than this anyway):
I am he as you are he as you are me
And we are all together
See how they run like pigs from a gun
See how they fly
I'm crying
Sitting on a cornflake
Waiting for the van to come
Corporation T-shirt, stupid bloody Tuesday
Man you've been a naughty boy
You let your face grow long
I am the eggman
They are the eggmen
I am the walrus
Goo goo g' joob
This song was written in a time when in general Western pop music was (in part thanks to these same Beatles) under a heavy influence of Eastern philosophy and drug inspired psychedelic movement, while at the same time the press was trying to scoop all kinds of dirt on the Beatles. One of the stories of the time was that Paul McCartney was dead.
This song, apart from having indeed a psychedelic tune, had lyrics that were meant to confuse people. It was supposedly one of a few attempts to make the press realize the futility in trying to unearth all kinds of stuff about the band; attempts that failed miserably, because the fact that Paul sang the line "I'm the walrus" was, ironically, seen as an indication that in fact, he must be dead! Another "hint" that he was dead was that on the famous Abbey Road album cover, he walked barefoot. And everybody knows that when dead people walk about, they don't wear shoes.
I wouldn't try to read too much into the lyrics, as they were never supposed to convey a real message other than "some of the things we say are nonsense, why can you press mosquitoes not accept that?"
That said, obviously the first line does allude to the Buddhist idea of oneness.