There must be some state or local law applied to every production of “Grease” going back 45 years, including every Broadway production, and every high school one, too (and the few million in between): Get “Greased Lightnin’ ” right.

Get it right, you’ve got ‘em for the next hour and a half. Get it wrong, and they head for the exits. (Except for the high school exits — you have no choice. You have to stay). Same with “Beauty School Dropout” — courtesy of Boyz II Men in Fox’s “Grease: Live” Sunday night. Also, the rousing opener, performed by British singer Jessie J, under a light California rain on the Warner lot. Or Rizzo’s “Look at Me, I’m Sandra Dee,” this version by Vanessa Hudgens, whose father died a few hours before.

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Also the “Dance Off” scene, and — of course — “Hopelessly Devoted to You,” performed by Julianne Hough’s Sandy. (And don’t ask me if that nice performance was dubbed, but we all have our suspicions.)

Get the music right — and this Fox version mostly did — and get the choreography right — and it entirely did — and you’ve got a winner. “Grease: Live” was maybe not a slam dunk, but nevertheless was the crowd pleaser it deserves to be and so often has been. For a lot of viewers Sunday — mostly pleased — that was more than good enough.

It certainly didn’t hurt that “Grease: Live” had at the helm one the hottest directors on Broadway at the moment — Thomas Kail, of “Hamilton” — who along with an excellent cast brought energy, drive and enough revisions and welcome updates — most notably a diverse cast — to almost make you forget the 1978 movie.

Almost, but some movies are never forgotten and this is one — unfortunately for Aaron Tveit (Danny) and Hough, who are no John Travolta or Olivia Newton-John, not that anyone is. With next to zero chemistry between the two, that left the heart of this “Grease” not always fully engaged. Both were certainly good, just not plausibly in “love,” and “Grease’” — like those summer dreams, ripped at the seams — is all about lost love, and the triumph of love. Or at least puppy love.