Producers used them almost as a "Where's Waldo" type of challenge for devoted Losties, sticking them on sports jerseys and bedside alarm clocks. They even served as the flight number for the doomed plane itself.
But did we really learn their significance? Probably not.
Sure, we found out how Jacob and the Man in Black (later to become the smoke monster) came to live on the island -- shocker, they're twins! -- when a recent episode revealed they had been born to a shipwrecked young mother and raised by an all-knowing woman who bashed the mother's head in shortly after she gave birth.
But when the young castaway questioned the island woman about where she came from, the woman simply brushed her off, saying, "Every question I answer will simply lead to another question."
It almost seemed to be a message from "Lost" producers, straight into the living rooms of the show's fans.
We never found out where Mother -- the woman who raised them -- wound up on the island or came to possess the power to protect it.
But as "Lost" ended, so did the epic battle between good and evil between Jacob and the Man in Black. Jacob faded as soon as Jack accepted his new role as island protector.
And Jack made good on his promise to kill the Man in Black inhabiting John Locke's body. Once Desmond extinguished the light, taking the Man in Black's powers along with it, Kate was able to shoot him in the back, followed by an assist over the cliff with Jack.
The only quibble with the finale? The Man in Black spent centuries trying to make it off the island, killing dozens and inspiring his twin brother to radically alter history for hundreds of people to keep him at bay.
And he's killed by a gunshot and a fall off the cliff. Seriously?
We've all known Desmond Hume was special from the very moment he came face to face with the survivors back in season one. And not just for his mega-watt grin and swoon-worthy accent.
Once the hatch-keeper, whose sole reason for existence was to push a button every 108 minutes -- there are those numbers again -- Desmond can withstand enormous quantities of the island's electromagnetic power even after others have died from the same exposure.
Charles Widmore, you know, before he was casually blown away by Ben, said Desmond was his "last resort."
And indeed, he was the last resort to saving the island from the Man in Black. It was Desmond's ability to withstand the electromagnetic energy to disable the island's powers long enough for the threat of evil to be extinguished.
Thanks, brutha. The universe owes you one.
This season's opener introduced the flash sideways. Because, you know, after years of figuring out flashbacks and flash forwards, viewers needed a little shake-up.
But as we got to see glimpses of a world we don't yet understand, we were also treated to a very quick flash of the island in a flash-sideways world -- deep under the ocean with a Dharma-branded shark circling overhead.
It was referenced several times in the first hour when Fake Locke threatened to sink the island. And after Desmond removed the cork from the well of light, we did indeed see portions of the cliffs plummet into the ocean.