In Los Angeles, stars including Morgan Freeman, Gary Oldman, Sterling K. Brown and Mandy Moore react to their Screen Actors Guild Award wins backstage, while also discussing the Time’s Up movement. (Jan. 22)

Spoiler alert: This story contains substantial details from Tuesday’s episode of This Is Us.

Even when This Is Us throws a party, it’s not exactly a stress-free event.

After all the grieving in recent episodes that centered on Jack Pearson’s death, the hit NBC drama tried to celebrate in Tuesday’s post-Olympics return. The wedding-themed episode featured present-day Las Vegas bachelor and bachelorette parties for Toby and Kate, and a Big 3-orchestrated anniversary party for Rebecca and Jack in the past.

Through much of “Vegas, Baby,” only Beth (Susan Kelechi Watson) had the proper let-your-hair-down attitude — and she revealed later in the episode that she was faking it. 

Beth and her husband, Randall (Sterling K. Brown), were in Las Vegas to attend the pre-wedding parties, but Randall was obsessing over the welfare of former foster child Deja (Lyric Ross), whose surprise visit in the post-Super Bowl episode was to ask for money to get the heat turned back on at the apartment she shares with her mother.

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Madison (Caitlin Thompson), left, planned the Las Vegas bachelorette party for her friend, Kate (Chrissy Metz) on Tuesday’s ‘This Is Us.’ (Photo: Ron Batzdorff, NBC)

Kate’s other brother, Kevin (Justin Hartley), was hardly the life of the party, either. He started by steeling himself to maintain sobriety in the Vegas party atmosphere, only to be depressed and tempted when he learned that his big role in a Ron Howard movie had been substantially cut.

Even Kate (Chrissy Metz) and her fiance, Toby (Chris Sullivan), appeared to have reservations about the event, with neither having cultivated many friends. 

In the past, the Big 3’s parents, Rebecca (Mandy Moore) and Jack (Milo Ventimiglia), fared substantially better, as they shared a romantic first anniversary at a bowling alley, with Jack arranging a spotlight dance for the couple. On their fourth anniversary, he surprised his pregnant wife with a piano.

By the 15th anniversary, when the Big 3 were 10, Rebecca, understandably overwhelmed by the gift-giving one-upmanship of sometimes too-perfect Jack, asked for a break from presents. But this time, the kids decided to throw their parents a bash.

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That didn’t start out well, as 10-year-old Kevin messed up elaborate dinner preparations and then stressed out thinking his parents were headed for divorce. They assured him they weren’t.

Back in Vegas, there was plenty of discomfort, too. Both Kevin and Randall departed early from the bachelor party, disappointing Toby, who was hoping to bond with his future brothers-in-law.

Randall, worried about Deja after a phone call, crashed the bachelorette party at Magic Mike Live, leading to a big fight with Beth when he suggested she was heartless. Kate upped the ante by taking her brother’s side and then blurting out, “Randall has made it perfectly clear who’s more important to him.”

As happens to be the formula on This Is Us, things worked out, at least for the most part, by the end of the hour. 

The second half of the Big 3’s present worked out better, as Jack and Rebecca found a path in their room, marked by…