Here's how old the stars of 'Grease' were compared to their characters' ages

• "Grease" was released on June 16, 1978.

• The film follows high schoolers during the 1958 school year, but no one in the cast was a teenager.

• John Travolta was 23 when playing Danny Zuko, but some of his costars were much older.

Max Kalnitz contributed reporting to an earlier version of this article.

While "Grease" focuses on the lives of high school students, the actors who played the principal characters had graduated from high school many years before filming.

Director Randal Kleiser told Vanity Fair he had to do a "crow's-feet" test to make sure none of the cast looked too old for the part.

"I would get up close to them and see if they had any crow's-feet around their eyes, and that would show they were beyond the surreal age that we had determined would work," he told Vanity Fair in 2016. "High-school kids could not have crow's-feet."

Keep reading to see each "Grease" star's actual age compared to that of their on-screen character.

Danny Zuko is 18 during his senior year at Rydell High School.

The film "Grease" is based on a 1971 musical of the same name. It focuses on the relationship of American high school student Danny Zuko and Australian vacationer Sandy Olsson, who fall in love during the summer but fear they won't see each other again.

When Sandy's parents decide not to return to Australia, she enrolls at Rydell High where Danny is the leader of the T-Birds greaser gang. After realizing they now attend the same school, Danny proves his "coolness" by making fun of her in front of his friends, prompting Sandy to join the Pink Ladies. After the two play a game of cat and mouse they finally confess their mutual love for one another.

John Travolta was 23 when "Grease" was filmed in 1977.

Although Sandy tells the Pink Ladies during "Summer Nights" that Danny "was sweet, just turned 18," Travolta was older than his character by a few years when filming.

However, Travolta — who had already starred in "Saturday Night Fever" when "Grease" came out — was still younger than some of his castmates.

Sandy Olsson, Danny's love interest, is 17 or 18 in "Grease."

After Danny messes things up, Sandy spends some time with the jock Tom but eventually realizes Danny is the one that she wants. At the end of the film, she dresses as a female T-Bird to win him back.

Olivia Newton-John turned 29 while filming "Grease."

The British-Australian singer-songwriter was more than 10 years older than her character while filming "Grease."

When Newton-John was cast for "Grease," she had almost no acting experience but was already a bona fide pop star, with five No. 1 hits on the Billboard Hot 100.

Newton-John died at 73 on August 8, 2022.

Betty Rizzo, leader of the Pink Ladies, is 18 in the movie.

Rizzo spends most of the movie acting as the tough leader of the female greaser gang. But when a rumor about a pregnancy scare starts to circulate through the halls of Rydell High School, she realizes she isn't as tough as she acts.

She was played by then-33-year-old Stockard Channing.

Channing was almost double the age of her "Grease" character. According to Vanity Fair, the 33-year-old actress "was the oldest of the principal actors cast."

Two years after the movie was released, she went on to star in her own sitcom, "The Stockard Channing Show."

Kenickie, second in command of the T-Birds, is also supposed to be 17 or 18 in the film.

Kenickie is Rizzo's love interest and is also the owner of the Greased Lightning car that Danny uses in the drag race against Leo, the leader of the T-Birds' rival gang, the Scorpions.

Actor Jeff Conaway was actually 26 at the time.

When Conaway starred in the Broadway rendition of "Grease" in the early '70s, he was much closer to the age Rydell High School students would have been. But at 26, Conaway graduated high school years before his on-screen character did.

Conaway died in 2011 at the age of 60.

Marty Maraschino, another member of the Pink Ladies, is supposed to be 17.

Marty spends the majority of the movie trying to act more mature than her fellow high school classmates and does so by flirting with older men, most notably Vince Fontaine, the host of Rydell's televised school dance.

She was played by the second-youngest main cast member, Dinah Manoff, who was 21 at the time.

Manoff was only older than Marty by four years, making her one of the actors closest in age to their characters in "Grease." It was her film debut.

Eighteen-year-old Sonny LaTierri is a wise-cracking member of the T-Birds who has a crush on Marty.

Sonny is equal parts cocky and stubborn. He's also a bit of a trickster – he spikes the punch at the school dance and doesn't hold back when making fun of the Pink Ladies.

Michael Tucci was the second-oldest cast member at 31.

Michael Tucci was over 10 years older than his character and older than all of his co-stars except Stockard Channing, who was 33.

Following his role in "Grease," Tucci appeared in multiple TV shows throughout the '80s and '90s including "People's Court," "Diagnosis: Murder," and "The Paper Chase."

The pink-haired Pink Ladies member Frenchy is also 17 or 18.

With just a few days left until graduation from Rydell High School, Frenchy drops out to enroll in beauty school and accidentally dyes her hair pink. Her most famous scene occurs when Frankie Avalon appears as her guardian angel and sings "Beauty School Dropout," which, paired with her pink hair, persuades her to return to Rydell.

Frenchy was played by Didi Conn, who was 26 while filming during the summer of 1977.

Conn had appeared in multiple TV shows and movies before hitting it big with "Grease."

The goofy T-Bird, Doody, is also 17 or 18.

Doody is the T-Birds' comedic relief. During the movie, he ends up with Frenchy and, based on her scrapbook, got his nickname for supposedly looking like the TV-famous puppet Howdy Doody.

Barry Pearl was 27 when he played Doody.

Prior to his stint as Doody, Pearl played Sonny in the 1973 musical tour, according to Lancaster Online.

Jan, a 17-year-old member of the Pink Ladies, had an affection for sweets and was dating Putzie.

Jan rocked iconic pigtails that helped convince audience members that she was a high school student.

Jamie Donnelly, who played Jan, was actually 30.

Donnelly told People in 1998 that she had to dye her prematurely gray hair to look the part of a high schooler.

The 17- or 18-year-old Putzie famously hits Kenickie in the head with his car door ahead of the T-Birds' drag race with the Scorpions.

Putzie is a bit clumsier and less cool than the other T-Birds. He famously says that Jan is a "cheap date," but she somehow takes it as a compliment and their relationship grows throughout the film.

Kelly Ward was the youngest of the main cast members at 20.

Ward was only two or three years older than his character, making for the most realistic portrayal of a high school student among the main cast.

Leo Balmudo, the leader of the T-Birds' rival gang, the Scorpions, was also 17 or 18.

Leo wasn't a Rydell student so he either attended St. Bernadette's with his girlfriend, Cha-Cha, or was a dropout.

He was played by Dennis Stewart, who turned 30 while filming "Grease."

Stewart was more than a decade older than his "Grease" character. In addition to starring in "Grease 2" in 1982, he appeared in numerous TV series through the early '90s.

Stewart died from complications from AIDS in 1994 at the age of 46.

Leo's girlfriend, Charlene "Cha-Cha" DiGregorio, is also 17 or 18 in the movie.

Cha-Cha is a student at a different school in town, St. Bernadette's. She says in the movie, "They call me Cha-Cha because I'm the best dancer at St. Bernadette's."

Actress Annette Charles was 29 at the time.

Following her role in "Grease" and a string of TV appearances in the '70s and '80s, the actress went back to school as Annette Cardona. She earned a bachelor's degree in psychology and theater from Antioch University Los Angeles and a master's degree in social work from New York University, according to California State University, Northridge, where she was a professor.

Cardona died in 2011 at the age of 63.

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