'Supernatural' Celebrates 300th Episode With a Heartbreaking Family Reunion

supernatural 300
The CW

The Winchester brothers got more than they bargained for in the milestone episode.

Warning: Spoiler alert! Do not proceed if you haven't watched Supernatural's 300th episode, titled "Lebanon."

Supernatural celebrated its 300th episode on Thursday by bringing Dad back from his hunting trip, if only for a few heartbreaking moments.

The milestone ep kicked off with the Brothers Winchester checking out the backroom of a sketchy pawn shop, where they encounter -- and ultimately swipe -- several occult items, including a pearl that Sam (Jared Padalecki) recognizes as an ancient Chinese treasure that grants "your heart's desire."

However, the brothers get more than they bargained for when Dean (Jensen Ackles) decides to use the mystical power in the hopes of banishing the archangel Michael from his head, but instead ends up summoning their dad, John Winchester (Jeffrey Dean Morgan), from 2003 to the present.

After some understandable confusion, and a tear-filled family reunion -- which includes John seeing his wife, Mary (Samantha Smith), for the first time since her death in 1983 -- the brothers fill their dad in on what's been happening in the years since his initial disappearance.

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"So, you saved the world. And now you live in a secret bunker with an angel and Lucifer's kid," John puts together, understandably baffled, but undeniably proud. "I just wish that I had been there to see it."

But of course, there are always consequences to messing with time, a lesson that Sam and Dean find out quickly when they venture into town to buy supplies for a family dinner. No one in Lebanon recognizes them, there's a wanted poster accusing Dean of assault, murder and credit card fraud, and a quick Google search reveals Sam is a TED Talk-giving, kale-loving CEO in California. (Plus, a still-alive Zachariah (Kurt Fuller) shows up with a murderous Castiel (Misha Collins), who doesn't recognize either of the brothers.)

"It's a temporal paradox," Sam puts together, realizing that their timeline has shifted after bringing John to the present -- and the only way to prevent the changes from becoming permanent is to send him back.

When the dilemma is presented to John, he realizes there's no choice to make -- especially when Mary's mortality is in jeopardy. The Winchesters enjoy one final family dinner together before saying their tearful goodbyes, savoring the moments they didn't get to enjoy the first time around.

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"I am so proud of you boys," John tells his sons, before taking his wife's hand one last time. "You two, you take care of each other."

"We always do," Sam assures him, as they crush the mystical pearl, sending their father back to 2003, where he wakes up in the Impala after "one hell of a dream."

The episode is Morgan's first return to the show in more than a decade -- The Walking Dead star last appeared onscreen as John Winchester at the end of season two in 2007, and his voice was briefly heard in the season three episode "Long Distance Call" in May 2008 -- and the actor celebrated the show's milestone and his return with a heartfelt Instagram post last month.

"Just so proud. Love everyone involved in this show. 300 episodes. Holy smokes," Morgan captioned his nostalgic shot. "Thank you to all you fans. Big love to cast and crew especially my (our) boys @jensenackles @jaredpadalecki you’re both amazing, and I’m not totally sure we all deserve you. Congratulations. Love. You’ve earned all of it."

Supernatural, which was recently renewed for its 15th season, airs Thursday at 8 p.m. ET/PT on The CW.