The show's co-creator Jim Jacobs wants to clue you in: You don't know Grease.

At least, not the Grease that he and Warren Casey created in Chicago back in 1971.

Jacobs likened the difference between that original Windy City production and the one that bowed in New York in 1972 to the divergent characters of John Gotti and Pee-Wee Herman. "It went from an in-your-face show about delinquents to a colorized gang of lovable people singing rock 'n' roll. It went from black jackets to pink jackets."

Jacobs told Chicago Tribune theatre writer Chris Jones about this while being interviewed in early 2009 about a national tour of the show that was then opening in Chicago. Jones asked the writer which of the many productions of Grease had been his favorite. Jacobs answered that he was still rather fond of the first one, which was staged at the now-vanished Kingston Mines community theatre. This caused Jones to write an article which challenged "Mr. and Mrs. Chicago Producers" to stage the first version of the musical. PJ Paparelli took up the challenge; a revival entitled The Original Grease will begin performances at American Theater Company (ATC) April 21.

"I got intrigued about this musical as a Chicago production," said Paparelli. Fortunately for him, Jacobs had kept the original script and score from that 1971 staging, which had run eight months at Kingston Mines. (Casey died in 1988.)

	PJ Paparelli

Jacobs and Casey, who were amateur actors at the time, had written the show as "the real nitty-gritty story of the kids I went to school with and the birth of rock 'n' roll," Jacobs told Playbill.com. The show was full of blue language and references to local Chicago landmarks. When producers acquired the rights and announced their wish to move it to New York, they asked for vast changes in the work.

"We cut the book to shreds, and added more singing and dancing," said Jacobs. "We had great fears the show wouldn't succeed" in New York. "We turned it from a three-fourths book, one-forth music show to the opposite — one-fourth book and three-fourths music."

Of course, the show did succeed — enormously. And the old Chicago version was forgotten. Until now.

For The Original Grease, Jacobs and Paparelli have brought back a lot of songs that were cut before the musical moved to New York, as well as some that were eliminated during 1971 Chicago rehearsals. "Warren and I had such a wealth of material to choose from," said Jacobs. "We wrote way too much."

"You're going to hear 'Greased Lighting' and 'We Go Together,'" said Paparelli. "But if you count them up, there are 13 new songs."

One specific instance: the well-known number "Summer Nights" will be replaced by its predecessor, "Foster Beach," which is named after a popular summer hangout on Lake Michigan. Producers made Jacobs and Casey change the song because nobody in New York would know about Foster Beach. Jacobs calls the number the "second or third cousin" of "Summer Nights."

Also, the book has been made significantly more specific and longer for the ATC production. "This one is more three-dimensional in terms of the relationships between the boys and the girls," said the author. "It's a real play and the songs stem out of that."

	Kelly Davis Wilson and Adrian Aguilar star in American Theater Company's Grease.

Also different is the language. These characters talk the way real teenagers do. "You had a taste of it in the New York company and it got cleaned up when we went to the Bible Belt," Jacobs said.

"I said to PJ that you're going to have to put in a sign in your box office saying this is R-rated," the writer said. "We know people are going to try and bring their kids. And I don't want them leaving saying, 'Oh we're so embarrassed, that was so un-P.C.' Well, I'm sorry — this is how it was."

Fans of the show won't be too disoriented. The plot, involving the interactions between a gang of male greasers and the Pink Ladies, is still basically the same, with bad boy Danny Zuko and new girl Sandy Dumbrowski engaging in a love-hate romantic dance. But "it's much more of an ensemble show," explained Jacobs, "instead of what Broadway did, which was to make Danny the super-cool hero and Sandy the special girl." Moreover, local Chicago references will be reinstated.

The changes informed the way The Original Grease was cast. Instead of looking for singers and dancers who could act, Paparelli and Jacobs went for actors who could sing and dance.

The run through June 26 has sold briskly. Whether the show will extend or transfer remains to be seen. Another open question is whether this old/new version will be licensed or recorded. "God only knows what will happen to it," said Jacobs.