Someone commented on a hidden meaning in the use of the Three Dog Night song in the episode Tricia Tanaka is dead.

When I was watching the watch lady explaining to Desmond how things were supposed to be (in the store, when she first tells him he's not supposed to buy the ring) as she ticks off the plot-points of his coming life, I kept thinking of the second verse of Mama Cass's song which go:

You're gonna be nowhere,
loneliest kind of lonely...

It was almost like the song was foretelling his time, alone, on the island.

added later: The song also sort of sums up Desmond's life. He (in his flashbacks) always seems to be giving up what he wants (make his own kind of music) because he is influenced by all the outside influences telling him what he "should" do and how he "should" act.

When he reawakens on the island and asks to be sent back again, it was like he was saying, "I won't be fooled again, this time. Please. Let me go back and I'll do it right this time." Like it had been some sort of a test and he failed it again.

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charlie98210
"Whoa!" she said. "Cry 'Havoc!' And let loose the dogs of war!"
And, like Banquo's ghost, they just won't go away.