This Is Us has emerged as the breakout new hourlong series of the fall 2016 broadcast season. Now Dan Fogelman’s sprawling ensemble dramedy, from 20th Century Fox TV, has received a Back 5 pickup from NBC for an 18-episode order, short of the standard 22.

This Is Us creator Fogelman had designed the heavily serialized, decades-spanning dramedy for shorter, cable-style seasons. I hear he originally was shooting for a 16-episode freshman season, with the number eventually adjusted up to 18.

“We are thrilled. This order for a complete first season of 18 episodes is exactly what we’d wanted and hoped for,” Fogelman said. “We’d carefully mapped out an 18-chapter story for the first year of the show, and this allows us to follow through with our exact initial intent. And to get the order so early on is a tremendous show of confidence and a boost for our entire cast and crew.”

The pickup comes ahead of the airing of This Is Us‘ second episode tonight. The dramedy’s premiere is projected to be the highest-rated new series debut during Premiere Week both in Live+Same Day and Live+3. It averaged a 4.2 rating in the demo (L3, up from 2.8 in L+SD) with 13.53 total viewers. After five days of playback, the averages grew to a 4.5 18-49 rating and 14.3 million viewers.

“It’s a rare moment in this business when a show so instantly delivers both critical acclaim and hit ratings, but This Is Us is just such an extraordinary achievement,” said NBC Entertainment president Jennifer Salke. “Creator Dan Fogelman, along with co-directors Glenn Ficarra and John Requa and the gifted producers, cast and crew, have delivered the kind of heart and depth that resonates with every segment of the audience, and we’re proud to extend its presence on our schedule.”

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This Is Us has been an anomaly all around. It was a spec script Fogelman took out shortly after moving to 20th TV following the cancellation of his ABC comedy The Neighbors. It was an off-cycle buy by NBC and an off-cycle pilot with no big stars or pre-sold title. But somehow, it stayed strong as pilot season progressed and landed one of the two best protected slots on the NBC schedule, behind The Voice on Tuesday. Then the trailer cut from the pilot for NBC’s upfront presentation took off online, amassing a staggering 125 million-plus views. And just a couple of days before the premiere, one of the This Is Us stars, Sterling K. Brown, won an Emmy for The People V. O.J. Simpson.

In addition to the highest-rated new series in L+3, with This Is Us, 20th TV also had the highest-rated entertainment program overall with Fox’s Empire (5.5) and promising new ABC drama Speechless.

The cast of This Is Us includes Milo Ventimiglia, Mandy Moore, Justin Hartley, Chrissy Metz, Sterling K. Brown, Susan Kelechi Watson, Chris Sullivan and Ron Cephas Jones. Fogelman serves as writer and executive producer with Don Todd. Jess Rosenthal, Charlie Gogolak and directors John Requa and Glenn Ficarra also executive produce.

NBC has been the quickest to hand out full-season orders this fall. On Friday, the network gave a Back 9 pickup to sophomore comedy Superstore. Its other fall comedy, freshman The Good Place, is designed for a 13-episode-season run.