'This Is Us' Season 4 Trailer Is Officially Here (and We Have So Many Questions)

This Is Us Season 4

In celebration of the Big 3's birthday, NBC dropped the official trailer for season four of This Is Us -- and it's a doozy.

Coming at over a minute, the new footage opens with young Jack (Milo Ventimiglia) and Rebecca (Mandy Moore) in the car as they wax poetic about how chance encounters with strangers can drastically change the trajectory of your life, setting up what's sure to be an interesting and expansive season.

"It's so strange, isn't it? How just like that a completely stranger can become a big part of your story," Rebecca says, as a vignette of new faces joining the This Is Us universe play throughout. "It's actually kind of terrifying, you know? How a single cross with one person who you've never met can change everything."

Primarily focusing on new cast additions like M. Night Shyamalan, Jennifer Morrison and Omar Epps (and seven other guest stars), the promo introduces a slew of big questions.

Like, how are these new characters -- whose details are being kept close to the vest -- connected to the Pearson family? What part of the family timeline do these mystery characters fall? Which Pearson family members do they interact with? Why are they significant? Sept. 24 can't come soon enough. 

Watch the season four trailer below.

"Our first episode, our universe fundamentally expands in a way that people might not be expecting," Mandy Moore hinted to ET's Keltie Knight at a This Is Us pancake breakfast in August.

Added co-star Justin Hartley, "Some new characters being introduced, some new relationships are going to be evolving."

Creator Dan Fogelman hinted that the way the season opens could be "potentially polarizing."

"In the series, we have what I call little markers, little stakes we put in the ground of these episodes that serve as grounding points for the whole arc and the whole series," he said. "Our first two episodes of this season are two of those and it's a big, bold, potentially polarizing -- but in the best possible way -- start to the season."

Last time we left the Pearson family, the season three finale raised several looming questions -- from the mystery of Rebecca's well-being to how Jack's younger brother, Nicky, comes back into the family's lives to the unclear fate of Kate in the future.

This Is Us is nominated for nine Emmys, including Outstanding Drama Series, and individual acting nominations for seven of its actors: Ventimiglia, Moore, Sterling K. Brown and Chris Sullivan, as well as guest stars Michael Angarano, Ron Cephas Jones and Phylicia Rashad.

This Is Us returns Tuesday, Sept. 24 at 9 p.m. ET/PT on NBC, with an extended premiere.

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