‘HSM’ 101

Predictions are always dangerous, especially in an election year, but if you are the parent or guardian of a child between the ages of 6 and 16, there is a trip to the cineplex in your very near future. In case you have somehow missed the magazine covers, billboards and general near-hysteria publicity, “High School Musical 3: Senior Year,” the third installment in the ridiculously successful Disney television-movie franchise, is a feature film, opening Friday. In a theater near you. Following the hopes, dreams and, of course, schemes and struggles of the now-famous cast of characters as they approach graduation, “High School Musical 3” is also a poignant parting of ways for a group of actors who catapulted to fame with the audience-inclusive mantra, and hit song, “We’re All in This Together.”

If history is any sort of barometer, this means not only serious popcorn expenditures but also that soon your house will be ringing with peppy songs suitable for either copycat or freestyle choreography and conversations in which the names Troy, Gabriella, Sharpay and Chad, not to mention Zac, Vanessa, Ashley and Corbin, will occur with alarming frequency. Many of you, no doubt, are fully prepared. Many of you are old hands at the “High School Musical” experience -- the opening night parties, the fights over who “gets to be” Gabriella, the muttered masculine admissions from older brothers that Troy and Chad are “kinda cool.”

Still, it’s a lot to keep track of, all those characters and the actors who play them, the whole biosphere of East High and the ethos of the Wildcats. So for those who don’t have time to revisit the first and second films but still want to be part of the conversation, we’ve prepared a short primer. And yes, this will all be on the final.

Troy and Gabriella

At the heart of “High School Musical” are these two young lovers played by Zac Efron and Vanessa Hudgens. Troy is the captain of Albuquerque’s East High basketball team, which is coached by his father (and that this is never perceived as a problem by anyone indicates the fairy-tale world of East High). Gabriella is an A-plus student with a scientific bent, the child of a single mother who has had to move around a lot for her job.

The two met on New Year’s Eve at a resort when they were thrown together in a karaoke contest and discovered not only each other but that They Could Sing. Imagine their surprise when Gabriella turned up as the new kid at East High! But the path of true love never does run smooth -- in the first film, members of the basketball and science teams conspire to keep the two apart and from auditioning for the school musical. For a minute it looks like it has worked. Gabriella tells Troy to take a hike. After a big personal-angst number from Gabriella, the plan backfires and ends in a huge climactic duet.

In the second film, the rich Sharpay (more on her later) tries to lure Troy away with a sweet summer job and the prospect of a basketball scholarship to the fictional University of Albuquerque. For a minute, it looks like it works. Gabriella tells him to take a hike. After a big personal-angst number from Troy, this too backfires and ends up in a huge climactic duet.

Good to know: Gabriella was named after screenwriter Peter Barsocchini’s daughter, who is now 14. Efron and Hudgens are indeed a romantic couple in real life, no matter what rumors to the contrary your child may have heard.

Behind the scenes: Between the first and second film, Efron chafed at being typecast as Troy and landed a role in “Hairspray.” With several other projects in the works, he returned to do No. 3 in a more positive frame of mind. Hudgens, meanwhile, had to cope with nude photos, taken and sent to a previous boyfriend, winding up on the Internet last year. As the photos were fairly tame, and an isolated incident, their appearance did not have any effect on her connection with Disney (and offered a valuable lesson in the dangers of transmitting nude photos of oneself electronically).

Sharpay and Ryan

Every fairy tale needs a villain, and Sharpay is it. Played with high-camp hilarity by Disney veteran Ashley Tisdale (“The Suite Life of Zack and Cody”), Sharpay is the school drama queen, literally, bagging all the leading roles (and some of the best numbers in each film) and setting her sights on Troy. At least until that, grrrrr, stupid Gabriella shows up. Rich and spoiled, Sharpay doesn’t love Troy so much as feel he is owed to her -- in her mind, they are the top kids in school. With her signature princess pink and portable pup, she flounces, squeals, grimaces and generally behaves like such a brat that some mothers may use her as an example of how not to behave. Though at the end of each movie she has a moment of revelation (Gabriella is a good singer, being in the spotlight isn’t everything) she forgets these lessons by the next movie.

Ryan (Lucas Grabeel) is her brother, and in the first film he was almost as scheming and pretentious as she was. But in “High School Musical 2,” he saw the light. When Sharpay coldbloodedly dumped him from a duet in the hopes of getting Troy involved, he made peace with his fellow Wildcats and revealed himself to be an excellent baseball player and choreographer.

Good to know: Sharpay’s dog, Manly, is actually owned by director Kenny Ortega. Although “owned” is probably not the best word for it. Manly is ever-present on set; when he’s not on the crook of Ortega’s arm, he has his own doggie stroller. The tensest day of shooting for “HSM3” was the day Manly went missing -- fortunately he was found safe and sound, but several Disney staff members lost years off their lives.

Behind the scenes: Between the second and third movies, Tisdale had work done on her nose, and her altered appearance will no doubt be the subject of much discussion.

Chad and Taylor

Best friends of Troy and Gabriella, Chad (Corbin Bleu) and Taylor (Monique Coleman) share their respective spheres of interest -- Chad is all about basketball, Taylor is a super-smart academic. They began to come together as a couple in the original “High School Musical” when they realized: (A) how mean-spirited their plans to divide Troy and Gabriella were, and (B) how hurtful cliques of any sort are. In the second film, Chad served as Troy’s nagging conscience when Troy seemed to be blowing off his friends in an attempt to ingratiate himself with Sharpay’s family and its University of Albuquerque contacts. (Parents may have had a different view of Troy’s behavior -- there was a college scholarship at stake, after all, and how terrible is it to miss an employee baseball game? Not so terrible.)

Good to know: Between the first and second movies, Bleu starred in “Jump In,” another Disney TV movie about a boxer who becomes a double-dutch champ. Although not a “High School Musical”-type hit, it was pretty darn good.

Behind the scenes: The stars, who are not a couple in real life, seem to live up to their squeaky-clean images.

Kelsi and Martha

Although she is the composer and lyricist of the group, Kelsi (Olesya Rulin) too often finds herself a pawn of the scheming Sharpay, who wants all the best songs for herself; she is also known for her large collection of hats. Martha (KayCee Stroh) made good use of a small (but exuberant) part in a big song during the first film; by the second, she had entered the inner circle.

Good to know: Salt Lake City is a stand-in for Albuquerque, but all the school interiors are shot at a real school, the mascot for which is a panther.

Behind the scenes: While she didn’t have to cope with the paparazzi who showed up to shoot Efron and Hudgens during the filming of “HSM3,” Rulin had her own frustrations -- being in Salt Lake during perfect powder conditions but unable to ski because of a standard contract clause.

Oh, and East High’s colors are white and red. In case you were wondering what you should wear to the movies.

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mary.mcnamara@latimes.com