NBC has handed its 2016 first-year hit, “This Is Us,” a two-season order for a total of 36 episodes. Loosely translated: “This is Us” is going to be with all of us for a considerable time to come.

In itself, a two-season order (with 18 episodes each) is not that unusual for a hit series, although a little less than usual for a freshman one. What is unusual are the parameters NBC has based this decision on: “This Is Us” is one of the most streamed series on network TV — or in the lexicon of TV-speak, its “live-plus-seven-day” numbers are record-breakers.

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The network said an average 14.6 million viewers watch the series on some platform over an average seven-day period after a Tuesday night episode airs. However, it didn’t even bother to cite figures for the platform that arguably matters most: the NBC network itself, where the increasingly old-fashioned “ratings” are still the only performance yardstick. In addition, NBC said the first 10 episodes this season had been viewed a total of 72 million times on those multiple platforms.

Most network series these days are evaluated — and ultimately renewed or canceled — based on their multiple viewing platform performance. “This Is Us” may well be the first to get a cherished two-season order based largely on its online performance.

The world of network TV is indeed changing.

Meanwhile, the show has cast Katie Couric and “Atlanta” star Brian Tyree Henry in guest roles for the second half of its first season, creator Dan Fogelman told TV critics Wednesday at their winter press tour in Beverly Hills, California. Couric will appear as herself in a segment where she interviews Justin Hartley’s character, Kevin, while Henry will play a character from William’s (Ron Cephas Jones) past, and appear in both the present day storyline and in flashbacks.