“Hairspray Live!” — NBC’s next musical based on the 2002 Broadway hit and airing Dec. 7 — has added Rosie O’Donnell to the cast, “Hairspray Live!” co-producer Craig Zadan announced at the TV Critics tour Tuesday.

Also, Sean Hayes will join the cast, he said.

Big news indeed for “Hairspray” fans, and now “Hairspray Live!” — which will return Harvey Fierstein to the role he memorably established on Broadway nearly 15 years ago, as Edna Turnblad — is nearly complete, as far as casting is concerned.

O’Donnell, who hails from Commack, will play the Gym Teacher (which Jackie Hoffman originated on Broadway) and Hayes will play Mr. Pinky, the dress shop owner.

Still to be cast are two key roles: Seaweed J. Stubbs, son of Motormouth Maybelle (played by Jennifer Hudson in the NBC production, and who was here Tuesday at the Tour), and his sister Little Inez. Both are vital roles in a production that’s at heart about race, racism, and integration. (Neither Zadan or co-producer Neil Meron had news on that casting front).

Also to be determined: Whether O’Donnell will also play a couple of other minor roles played by Hoffman in the original Broadway production.

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Here’s where the cast stands at the moment: Tracy Turnblad will be played by newcomer Maddie Baillio; Kristin Chenoweth is Velma Von Tussle (famed or infamed “Hairspray” villain); Ariana Grande is Tracy pal Penny Pingleton; Disney Channel star Dove Cameron (“Liv and Maddie”) is stage brat Amber Von Tussle (who was played long ago by Laura Bell Bundy); Martin Short is Tracy’s nice-guy dad, Wilbur; and last but hardly least, Derek Hough is Corny Collins, host of Baltimore TV dance show, “The Corny Collins Show.”

“Hairspray” — which you already know but just in case — was one of the great Broadway musical successes of this century, with music by Marc Shaiman and lyrics by Scott Wittman. (Also winner of eight Tony awards.)

The NBC production — unlike the network’s previous two live musicals that were telecast from Bethpage’s Grumman Studios — will originate from the Universal Studios lot in Universal City, California.