All Along The Watchtowersupernatural : Season 1... Instant

: It finally resolves the pregnancy of Kelly Kline with the birth of Jack , a character who becomes central to the series' remaining seasons.

: The story introduces a "tear in space-time" leading to an alternate reality —a bleak world where the Winchesters were never born and the war between angels and demons has devastated the planet. All Along the WatchtowerSupernatural : Season 1...

: The episode features the heartbreaking deaths of major characters, including Crowley , who sacrifices himself to trap Lucifer, and Castiel , who is shockingly killed by Lucifer. : It finally resolves the pregnancy of Kelly