This week, “This Is Us” delivered the Déjà-centric episode we all needed, “Modern Family” fished out the low-stakes half-hour it does so well, and “Young Sheldon” genuinely tried to rescue itself from its recent string of formulaic plots.

‘This Is Us’

“This Is Us” is a show deeply rooted in time. So far, it has used a variety of color palettes, makeup and hairstyles to carefully distinguish the different timelines that it seeks to explore. Because “This Is Us” has demarcated the streams of the past (and future) that it swims in, it can pull off an episode like “This Big, Amazing, Beautiful Life” — which loops forward, backward and all around through time — without sacrificing coherence or clarity.

“This Big, Amazing, Beautiful Life” takes a deep dive into Déjà’s (Lyric Ross) untold backstory. We watch with frustration as she grows up under the care of a confused and sometimes selfish mother, we wince with fear as she gets taken into foster care because of her mother’s negligence, we cry out with joy when she finally meets up with Randall (Sterling K. Brown) and Beth (Susan Kelechi Watson), and we sigh with resignation when her largely unchanged mother comes back for her.

These big moments in Déjà’s life are peppered with fleeting glimpses of the lives of the main cast. When Déjà’s great-grandmother reads her a bedtime story, there is also a quick montage of Rebecca (Mandy Moore) and Randall reading their kids the same story. When she sees her foster parent hitting her foster sister, there is a small cut to Jack’s (Joaquin Obradors) father hitting him and his brother.

The success of “This Is Us” rests on its portrayal of a shared human experience. Even though Déjà’s life couldn’t be more different from those of the Big Three, they are still united by the emotions they have felt — be they love, anger, grief or happiness. As Déjà later says, everybody’s got “things that hurt them, things that make them feel better.” Seeing her story in conjunction with little vignettes of the other characters’ stories is a testament to that shared experience, that broad spectrum of emotions somehow connecting all of us, no matter our differences.

Most importantly, the episode provides the showcase that Lyric Ross deserves.

There is an indescribable expressiveness to Ross. She packs in quiet heartbreak, innocence and simmering anger all in one beat. In less than a season, Ross’s emotional range has made Déjà’s character as well-rounded and fleshed out as any of the other Pearsons.

All signs portend to Déjà officially becoming a member of the Pearson clan. Let’s hope that happens as soon as possible.

‘Modern Family’

“Spanks for the Memories” is a fun stand-alone episode of “Modern Family.” Jay (Ed O’Neill) continues to display his surprising earnestness from “Written in the Stars,” Phil (Ty Burrell) and Alex (Ariel Winter) have an insightful conversation about the challenges that college students have to face, and Cam (Eric Stonestreet) and Mitch (Jesse Tyler Ferguson) partake in another one of their slapstick comedies of error.

The central misunderstanding in this episode occurs when Jay overhears a phone conversation between Gloria (Sofía Vergara) and her friend and mistakenly assumes that she is unsatisfied with their sex life. Predictably, this leads to a lot of crossed wires and mixed signals that eventually culminate in a standout moment of actual communication between the couple.

Most family-themed sitcoms don’t necessarily have many honest conversations about sex. It is a welcome bit of change, then, to see Gloria and Jay actively sharing their needs and wants.

While Jay and Gloria are figuring things out, Alex expresses her stress about an internship by relentlessly babying and bullying her dad. Phil easily sees through Alex, and he reassures her worries about not actually wanting the job she fought so hard to get. We all know that Phil is a goofball, but conversations like these are important reminders of his parental maturity. Alex, too, continues to serve as a grounded representation of a college student’s insecurities. “Modern Family” just needs to give her more opportunities to explore storylines that don’t rely on her trademark intelligence and sarcasm.

Elsewhere, Cam and Mitch are off in another of their breezy, entertaining capers. This time, they have to hide the fact that Mitch lost his job from their friends, who are over for a soiree. Watching Cam and Mitch work together to scheme is always entertaining, mostly because their plans almost always end in flames.

Overall, “Spanks for the Memories” is a well-rounded and low-stakes half-hour of “Modern Family,” which seems to have reignited the comedic spark that burned out last season.

‘Young Sheldon’

“Dolomite, Apple Slices, and a Mystery Woman” is a return to form from the tiresome descent into mediocrity “Young Sheldon” was hellbent on taking. Besides introducing a potentially recurring character, Libby (Anjelika Washington), the episode also brings back Jim Parsons’ voice-over in a welcome storybook-like form.

As with other “Young Sheldon” episodes, there aren’t any side plots for the supporting characters in this latest installment. It just focuses on Sheldon (Iain Armitage) as he gets to know Libby, his new school friend.

Libby is a welcome change to the two-man show that is Sheldon and Tam’s (Ryan Phuong) friendship. Tam, who used to be a multidimensional character grounded by his experience as an immigrant, has recently just become a hornier, 16-year-old version of Sheldon.

Libby’s inclusion in the group is therefore much-needed because it adds a different perspective to the increasingly similar dynamic between Sheldon and the supporting cast. The show needs Libby to explore other female characters who happen to be as academically ambitious as either Sheldon or Tam.

It is beyond adorable to see the 9-year-old Sheldon establishing a “mental rapport” with Libby. Their geology-filled discussions are bemusing to everybody else, but it’s apparent why Sheldon likes the new person in his life. He can pretty much talk about everything that interests him with Tam. With Libby, however, he gets to explore different sciences, different social mores and a different friendship. The scene where Libby keeps a lookout for Sheldon as he goes to the bathroom is just the right mix of silly and cute.

Of course, Sheldon’s burgeoning feelings for Libby come to a grinding halt when he realizes that she merely sees him as a young friend.

Even though Mary (Zoe Perry) does comfort Sheldon at the episode’s end, and even though it seems as if everybody is back to normal in Sheldon’s life by the end of the episode, it was still necessary that he experience what he did. After all, a part of growing up is reckoning with new feelings that you haven’t quiet felt yet, whether that emotion is your first crush or your first bout with heartache.

The willingness of “Young Sheldon” to portray genuine depth after a prolonged stretch of triteness is hopefully a sign of better things to come.