Olivia Newton-John as Sandy in Grease

Grease is one of the biggest movie musicals of all time. Sure, the nostalgic 1978 film is a quotable singalong classic and slumber party favorite that made John Travolta and Olivia Newton-John into superstars, but it’s also a juggernaut of the teen movie genre, right up there with Clueless, Mean Girls, and Ferris Bueller’s Day Of. Like any great teen flick, the plot of Grease is appropriately low-stakes and narrow in reach, concerning the fleeting social lives of less than a dozen teenagers, most of them members of the T-Birds and the Pink Ladies, who benignly reign over Rydell High in the 1958–59 school year and do stuff like go to drive-in movies, drink ice cream sodas, and dance.

Seeing as how characters break into song and fly a car into the sky, Grease isn’t the most realistic movie, a concept that extends to its cast. Nobody in this pillar of teen cinema was actually of high-school age when the movie was shot over the course of 1977. Here’s how old the teenagers of Grease actually were when they made the movie.

John Travolta (Danny)

John Travolta as Danny Zuko in Grease

While Olivia Newton-John was already well-known prior to her starring role in Grease, John Travolta was probably the biggest box office draw in the movie, particularly as far as his hordes of young fans — the target market — were concerned. From 1975 on, the guy who would go on to play Danny Zuko, became one of the biggest teen stars around from his performance as the Danny Zuko-like Vinnie Barbarino, a dopey but tough high school student on the sitcom Welcome Back, Kotter.

In 1977, Travolta’s film acting career took off with Saturday Night Fever, where he played another likable bad boy, a disco-dancing, twenty-something New Yorker named Tony Manero. By the time Travolta had returned to once again playing a high school miscreant, this time in Grease, he’d already had his first Academy Award nomination (for Fever) under his belt. The music showed the world that Travolta could act, dance, and sing (although he’d proven that a bit with his 1976 top-10 hit "Let Her In"). And Travolta did it all at the tender age of 23.

Olivia Newton-John (Sandy)

Grease was the top-grossing film of 1978, and as such, it increased the visibility and star power of many of its cast members. Olivia Newton-John, however, was already extremely famous. Of course, her portrayal sweet and naive Sandy Olsson, who develops a tender romance with Danny Zuko (John Travolta) over the course of many summer nights, cemented her as a screen legend. But her transformation into a leather queen at the end of the film was even more inexplicable given her wholesome image in the music world.

When Newton-John landed the role in Greaserewritten for her, so that the character transferred to Rydell from Australia, not another American place — she was already a pop star. She’d scored nine #1 hits on the adult contemporary chart stretching back to 1971, including "I Honestly Love You" and "Have You Never Been Mellow." Newton-John only looked young when she played Sandy, a role she landed for her vocal skills and marketability, and she had barely acted before, only in the Australian musicals Toomorrow and Funny Things Happen Down Under. She was 29 years old when she played high-school senior Sandy in Grease.

Stockard Channing (Rizzo)

Grease‘s whole storyline featuring secondary female protagonist Betty Rizzo, or just Rizzo, leader of the Pink Ladies, is provocative for both the film’s 1950s setting and 1978 release. Rizzo refuses to play into society’s expectation that young women remain chaste and innocent, preferring instead to seek out physical gratification and being unashamed about it. (Her big solo number, "There Are Worse Things I Can Do," is all about that.) She winds up experiencing a pregnancy scare, but it’s all fine by the end of the movie.

Perhaps the edginess of Rizzo’s arc — or the consequence she may face because of it, in the form of teenage pregnancy "out of wedlock" as it would be put in the ’50s — just may never have seemed all that serious to some viewers, because actor Stockard Channing was so clearly not a teenager. In fact, according to Vanity Fair, Channing, at 33 years old, "was the oldest of the principal actors cast" when Grease went before cameras in 1977. That made her almost double that of her character, a high school senior assumed to be 17 or 18. Grease takes place in 1959, and Channing brought real-life experience to the part, seeing as how she actually was still in high school at the time.

Jeff Conaway (Kenickie)

Portraying Kenickie in Grease, the Rizzo-loving and most outwardly criminal and nefarious of the overall harmless T-Bird gang, was the breakout movie role for actor Jeff Conaway. To that point, he’d landed small roles on Happy Days and The Mary Tyler Moore Show, and movies including The Eagle Has Landed and Pete’s Dragon. Grease just happened to be the perfect transitionary role for Conaway, a seasoned and accomplished stage actor. He was actually a cast member in the original Broadway stage production of Grease in the early ’70s, serving as understudy and eventually taking on the lead role of Danny Zuko.

The film version of Grease hit theaters in 1978, just a couple of months before the debut of the sitcom Taxi, where Conaway would star as wannabe actor Bobby Wheeler for three seasons before leaving the show in search of better opportunities. Conaway frequently worked in movies and TV into the 2010s while also struggling with substance abuse issues — he died at age 60 in 2011. Grease is probably the project for which Conaway will be most fondly remembered, by both fans and his castmates. In fact, Stockard Channing even told Watch What Happens Live that Conaway was "the horniest" of the fake teens. "[His] trailer would be rocking at lunch time," she recalled. Taking into account Los Angeles Magazine‘s shooting timeline for the film as "between June and September of 1977," and with Conaway’s birthday being Oct. 5, 1950, when he played teenage sort-of-hoodlum Kenickie, he was already 26 years old.

Barry Pearl (Doody)

The central plot of Grease — the will-they-or-won’t-they coupling of Sandy and Danny — is a complicated one and takes an entire school year to resolve. A big part of why Danny messes it up is because he pays too much attention to the opinions of his friends, a bunch of silly goof-offs who think they’re a gang because they call themselves the "T-Birds" and wear leather jackets. Chief among this group is Antony DelFuego, primarily known as Doody, a guy who wields a squirt guns and likes to look up girls’ skirts. In the 1978 film of Grease, he’s portrayed by actor Barry Pearl, a man who has done a lot of Grease. His first taste came via the national touring production of the Broadway version — which helped spread the show’s popularity and built interest in the film. In that iteration, Pearl played a different T-Bird, Sonny. In 2016, he was cast in a cameo role in Fox’s Grease Live television event as Stan Weaver, agent for dance TV show host Vince Fontaine. But Pearl’s most famous Grease is the 1978 big-screen movie version, of course. He’d landed small roles on a handful of TV shows and films before appearing as teenager Doody at the ripe old age of 27.

Michael Tucci (Sonny)

Sonny (real name: Martin LaTierri) thinks he’s bad to the bone because he’s part of the T-Birds, the self-proclaimed roughest of the rough at Rydell High School. He does spike the punch at the big dance-off, and claims to not suffer fools… except for when he’s actually placed into a situation involving confrontation and he sheepishly backs down, such as when he’s stared down by Rydell’s Principal McGee. Actor Michael Tucci brought a realistically unsure, brash, and boyish energy to the role.

Tucci appeared occasionally in films after Grease, including roles as Chico Marx in the Groucho Marx biopic Groucho, and as the father of Melissa McCarthy’s character in The Heat, but he built up an extensive resume of appearances on 1980s and 1990s television. For example, he was the title character’s neurotic best friend Pete on It’s Garry Shandling’s Show and played hospital administrator Norman Briggs on Diagnosis Murder. Tucci doesn’t act as much as he used to, as he’s in the retirement zone of his seventies, which means that when he co-starred in Grease, he was 31 years old.

Kelly Ward (Putzie)

Putzie is one of T-Birds leader Danny Zuko’s closest friends and compatriots — he’s the blond one with the appropriately retro ducktail haircut. He’s a bit of an oddball, as his big moments are hitting Kenickie in the head with a car door and somehow romancing Jan after accidentally labeling her a "cheap date" at the Frosty Palace. (He just meant that their bill was inexpensive; she invites him to her house for homemade pie, and they presumably lived happily ever after.)

Prior to portraying Putzie in Grease, a role not in the original Broadway show and created just for the movie, actor Kelly Ward was best known for his supporting role in The Boy in the Plastic Bubble, a hit made-for-TV movie starring his future Grease cohort John Travolta. Ward is forever young on film. In 1983, just five years after the release of Grease, Ward quit live-action acting (he also appeared in episodes of M*A*S*H, The Waltons, and Magnum, P.I.) in favor of voiceover and behind-the-scenes work. Ward’s most prominent film role of Putzie in Grease arrived when he was 20 years old.

Didi Conn (Frenchy)

Unlike her friends and fellow Pink Ladies gang members, Francesca Facciano aka Frenchy isn’t too concerned with the overdramatic machinations and fallouts of the romantic entanglements of Rydell High’s senior class. She has bigger dreams in mind, so ready to get on with her life, following her dreams, and earning a living, that she drops out of Rydell a few before graduation in order to enroll in beauty school and become a hairdresser. After dying her hair blond and then accidentally pink (briefly transforming her into, quite literally, a Pink Lady), she realizes that she should turn in her teasing comb and go back to high school. That motivation comes from "Beauty School Dropout," one of Grease‘s central and most memorable production numbers, featuring ’50s star Frankie Avalon as "Teen Angel," delivering harsh advice to a star-struck Frenchy.

Before portraying 1950s teen Frenchy in Grease, actor Didi Conn had a little preparation, portraying 1950s inhabitant Joyce in an episode of Happy Days. Beyond that, she was best known for inexplicably disappearing in Grease 2, followed by her regular role on the short-lived sitcom The Practice, When Conn donned the pink wig to play Frenchy in Grease, she turned 26 years old during production of the film.

Jamie Donnelly (Jan)

One person from the smash hit early 1970s Broadway run of Grease who reprised the role they played on stage for the 1978 film version: Jamie Donnelly, who helped originate the role of Jan, the Pink Ladies’ comic relief. Her comedic stylings included singing along with, and imitating, a vintage TV commercial during a sleepover. Her other notable character trait is that she harbored an amusing fixation with junk food. Beyond Grease, Donnelly made other Broadway history, starring as Magenta and other roles in the original 1975 stage production of The Rocky Horror Show.

The Grease film represented Donnelly’s big break into screen acting, but the performer walked away. After the film, she started a theater in Kentucky and then became a Los Angeles-based acting coach, according to People. When Grease began filming in 1977, Donnelly had to "[dye] her prematurely gray hair" so she’d look like a high school kid. It’s humorous and ironic that Jan, the most outwardly and immature of the Pink Ladies, was portrayed by one of the oldest actors in the cast — Donnelly had just entered her 30s.

Dinah Manoff (Marty)

While the other Pink Ladies of Grease spend most of the film obsessing over teenage boys more or less their own ages, Marty would much rather pursue full-grown men — which all falls in line with her character wanting to appear more grown-up and more mature than her teenage age would indicate. During the taping of the TV dance show where chaos breaks out and relationships split wide open for those around her, Marty bides her time and flirts heavily with the show’s host, Vince Fontaine (portrayed by actual 1950s celebrity Edd "Kookie" Byrnes). She suggestively sucks on a lollipop and tells him her name is Marty Maraschino, "like the cherry." All that discomfort of a teen and an adult man circling each other is offset a little by the fact that Dinah Manoff, the actress who played Marty, was safely ensconced in the age of majority. When Manoff filmed her scenes for Grease in 1977, she was a relative newcomer to Hollywood, playing a couple of roles in made-for-TV movies and guest-star parts on Welcome Back, Kotter (with Grease‘s John Travolta) and Family (featuring her future Empty Nest castmate Kristy McNichol). Grease was Manoff’s first feature film role, and she was 21 years old when she secured the role.

Annette Charles (Cha Cha)

Charlene DiGregorio doesn’t have all that much screen time in the film version of Grease, but her appearance is both memorable and vital to the plot. The character is much better known as "Cha-Cha," a reference to both her first name and how she’s the self-proclaimed "best dancer at St. Bernadette’s," although she gets to attend the big dance TV show taping at Rydell High. Kenickie brings her as his date to make Rizzo, his one and only and with whom he’s on the outs, jealous. She also backs up her claims of being a really good dancer, showing off and showing up most of the main characters, bringing Broadway-quality chops to the big gym floor dance numbers. She was precociously talented and self-assured, for a high school, which likely came on account of how the actress who played Cha-Cha was 29 years old at the time of filming.

Cha-Cha was the most famous role on the resume of actress Annette Charles, who before Grease had landed guest-star roles on ’70s TV shows like Emergency! and Barnaby Jones. Except for a small role in the 2009 B-movie Transylmania, Charles walked away from screen acting in 1987. The actor passed away from cancer in 2011 at age 63.

Eddie Deezen (Eugene)

Movies set in the 1950s didn’t only solidify the enduring cultural cliches of "greaser" and "poodle-skirt-wearing goody-goody," it also helped codify what a nerd out to look, act, and sound like on screen. Rydell High’s king nerd Eugene Felsnic is the prototypical and definitive nerd in many ways — he’s naive, studious, bullied, lacks self-awareness, wears glasses, and talks in a nasally voice. In other words, he possesses all the hallmarks of nerds in ’80s movies and beyond, and many times those roles were portrayed by the same guy who played Eugene in Grease. Eddie Deezen played by-the-books young nerds in WarGames, Zapped!, Grease 2, and The Polar Express, among others.

Grease hit movie theaters in 1978, which was a breakthrough year for Deezen. He starred in two other movies that year, the low-budget Lasterblast (made famous when it aired on Mystery Science Theater 3000) and the cult hit Beatles-themed I Wanna Hold Your Hand. When he played high school-age dweeb Eugene in Grease, Deezen was barely older, just 20 years old at the time of the film, and one of the youngest members of the main cast.