Season: 3
Air Date: 5/23/07 

Yes, LOST is on here twice. Is that a cheat? Maybe, but love it or hate it, LOST is inarguably one of the most significant series of this generation and the greater overall TV conversation. Is it surprising that the most emulated series of the past five years would have more than one noteworthy finale? Is it surprising that one of those finales could also be viable for GOAT status? It shouldn't be.

LOST didn't create the flashback narrative technique, of course, but it mastered it in an impressive manner that spawned much acclaim and imitation. It also threatened to suffocate the show. Three seasons in, it was painfully clear that creators Damon Lindelof and Carlton Cuse were straining to continue to create character-centric flashbacks that resonated and enriched the castaways back-stories. Flat tales like the story nobody really wanted to know about Jack's tattoos, Locke being a gullible fool for the 47th time, or Sayid facing a personification of his shady past yet again left the once rapturous audience bored, while others were saddled with increasingly ridiculous additions to their bios (Kate was once married? Desmond was a monk?).

So how did Lindelof and Cuse rejuvenate the series? By abandoning their bread-and-butter format for a bolder one, and setting an end date for the series that would effectively kill all wheel-spinning in favor of renewed momentum and the promise that all of the island shenanigans would build to an actual, straightforward conclusion. The declaration that LOST was back in the game would be summed up with one game-changing scene: a Jack flashback that ended with a mysterious meet-up with a woman who would turn out to be...Kate?!

The intrigue doesn't stop there, as the flash-forward(!) ends with a future, despondent, alcoholic Jack screaming that they "have to go back." For three seasons we figured the series' end-game would center on the castaways finally getting off the island; the reveal that there was much, much more at stake was simply ingenious.

The masterful twist wasn't the only aspect that makes "Through the Looking Glass" an instant classic. The on-island events are just as, if not more, poignant, as the castaways finally take down the antagonistic island cabal The Others, and set the stage for a rescue team that we discover may have more sinister plans in mind. All of the action is underscored by Charlie's underwater sacrifice to point the "rescuers" in the right direction, as the series sends off one of its most beloved characters in a fittingly emotional fashion. LOST would still have its problems during its final three years, but this is the episode that convinced many to stay with it, while convincing the rest of us that we were watching something truly historic unfold.