Scene from “30 Rock” live show in 2010. (screengrab from NBC)

Cast member Alec Baldwin broke the news to celebrity suck-up show “Extra.”

Last time “30 Rock” did a live episode, back in October of 2010, it scored 6.6 million viewers -- a nice jump from the 5 mil of the week previous. This season to date, the series is averaging 4.8 million viewers.

Even more than in ’10, NBC is struggling for ways to grow its numbers, particularly during sweep ratings periods. And, because Betty White is too busy doing her own NBC show these days, “30 Rock” will once again use this other bright shiny light to attract viewers.

The idea for the show’s first live episode sprang from a live staged reading the program gave much earlier at the Upright Citizens Brigade Theatre in New York -- a fundraiser for the Writers Guild strike fund during the writers’ strike.

But, live prime-time episodes were nothing new at NBC, even then. Way back in September of 1997, “ER’s” season debut was performed live. It averaged nearly 43 million viewers, which was only 22 percent better than the non-live season-debut audience of 35 million one year earlier.

Yes, that’s how many people used to watch NBC.