'This Is Us' Fans React to Old Jack Pearson

This Is Us brought Jack back from dead... at least for one scene.

During the opening minutes of Tuesday's season finale, viewers got to see a heartbreaking "What If" moment featuring an older, and not dead, Jack Pearson (Milo Ventimiglia) renewing his vows to soulmate Rebecca (Mandy Moore).

In the scene, adult versions of the family can be seen standing as Rebecca walks down the aisle in a beautiful white gown, with Jack looking on.

Even at the brief glance of Jack, Fans were quick to express their grief for the fallen character.

JACK?!?!?!?!?! #ThisIsUs pic.twitter.com/3LtJqd1civ

— chelby (@chelbs99) March 7, 2018

Old Jack?? #ThisIsUs pic.twitter.com/UfPQDm6ev2

— Oscar (@dampcharisma) March 7, 2018

I lost my tears right in the beginning seeing Jack and Rebecca so I'm done already. 😭😭😍 #ThisIsUs

— Ourania Kourelias (@Ouraniaxo) March 14, 2018

Later in the episode, This Is Us further played with viewers' emotions seeing Jack and Rebecca's crenewal ceremony, including mentions of the couple opening their dream construction company, Big Three Homes, which they planned to open before the fire.

The show also showed a reception for the ceremony, then revealing the moment was a dream sequence from Kate's imagination.

Fans were further broken hearted, wishing Jack Pearson could have been there for Kate on the day of her wedding.

How great is @NBCThisisUs and @ThisIsUsWriters to give us Jack and Rebecca renewing their vows?! What a happy couple celebrating a long and happy marriage! @MiloVentimiglia @TheMandyMoore #ThisIsUs pic.twitter.com/jaFmw67rGd

— TheNerdyGirlExpress (@thenerdygirlexp) March 14, 2018

Flashback & forwards of Rebecca and Jack, their love story? Is why I cannot get her w Miguel #ThisIsUs

— Amelia (@Mrs_Amelia) March 14, 2018

Yo! I’m crying with Jack and Kate having an imaginary vow renewal ceremony on #ThisIsUs

— Tiffany (@tiffanyrj) March 14, 2018

@TheMandyMoore @MiloVentimiglia Rebecca singing to Jack #Moonshadow. Jack starts tearing up.

I start tearing up. Again. #ThisIsUs

— Marisa Tigney (@LovelymarisaT) March 14, 2018

Old Man Jack is making me cry big ugly thug tears. This is a show of pain. #ThisIsUs

— Lady Stoneheart (@LSHNorthAF) March 14, 2018

This Is Us previously teased Jack's return for Kate's wedding, leading fans to speculate what twist the drama might pull off next.

"We're not playing any games, but I will say that seeing him was one of the most visceral punches that I think we ever had. It's so powerful and poignant and haunting and tragic all at once," Aptaker said.

Aptaker said the goal of the finale, as far past the writers were concerned was to create an episode that has a sense of "hope and joy and optimism" after season that was "so marked by grief and tragedy and mourning."

Ventimiglia said fans would find out almost immediately why Jack makes an appearance in the finale.

"You will know why I am in aged Jack makeup," Ventimiglia told Entertainment Tonight at SXSW in Austin, Texas. "I don't want to tease anything other than you've seen the photos. Just be excited and enjoy."