These aren’t yet the scary characters that you know when Sulley, left, and Mike meet in “Monsters University.” (Pixar)

Pixar has a pretty solid track record when it comes to sequels. Like the Energizer Bunny, “Toy Story” just keeps going and going, with a fourth chapter of the hit franchise said to be in development. But until “Monsters University,” a new origin story set several years before the action of “Monsters, Inc.,” the acclaimed animation shop had never attempted a prequel.

You wonder what took them so long, because the characters Mike (voice of Billy Crystal) and Sulley (John Goodman) are funny enough and their relationship rich enough to make the back story worth telling.

The result is a charming addition to the “Monsters” canon.

Set at the titular Monsters University, the film is the story of how freshmen monsters Mike and Sulley — aspiring students of the fine art of scaring — met and became fast friends. It’s also the story of how they became, more essentially, themselves. Where “Monsters, Inc.” was a heavily plot-driven tale, “Monsters University” is a two-man, er, two-monster, character study.

When the film opens, they are not exactly the characters we know and love from the 2001 film. Mike is much more wide-eyed and innocent; Sulley is, to put it bluntly, a huge jerk. And they don’t exactly like each other.

From a narrative standpoint, it’s the exact opposite of “X-Men: First Class,” which tried to explain how young Charles Xavier (James McAvoy) and Erik Lensherr, a.k.a. Magneto (Michael Fassbender), grew up to become mortal enemies.

Monsters University gets underway when Mike, the tiny, cyclopean chartreuse-skinned cueball, and Sulley, the jumbo-size, furry blue beast, are both kicked out of the scaring department at M.U., where they’ve enrolled to learn how to make kids scream. As in the first film, children’s emotions supply the power grid of the monsters’ universe, accessible only through closet doors in children’s bedrooms.

In Sulley’s case, the expulsion is because he’s lazy and arrogant, a stuck-up legacy kid whose father was a school hotshot and who thinks he can simply coast through his coursework because of his family connections. In Mike’s case, it’s because he’s just not scary.

The academic setback affords director Dan Scanlon (who wrote the screenplay with Robert L. Baird and Daniel Gerson) the opportunity to introduce a few new characters.

In order to get back into the scaring program, Mike and Sulley are forced to team with a fraternity of losers to compete in the Scare Games, a campus-wide competition. If they win, they’ll be accepted back in the department. If they lose, they’re not just out of the department, but out of the school for good.

The other members of the frat (voiced by Sean Hayes, Dave Foley, Charlie Day and others) are cute, but they make a less than indelible impression. Helen Mirren is more memorable as the imposing, bat-winged Dean Hardscrabble, in whose hands Mike and Sulley’s fate rests. Aubrey Plaza contributes an amusing cameo performance as the sardonic, slightly goth president of the Greek Council, which oversees the Scare Games.

Of course, all the collegiate trappings — fraternities, cliques, athletic rivalries, academic struggles — are in-jokes mainly for Mom and Dad’s benefit. What does a kid know about keggers and dorm life? Young viewers, however, should appreciate the lessons about cooperation, hard work and honesty that underlie Mike and Sulley’s coming of age.

Crystal, 65, and Goodman, 61, are a long time out of college, but they somehow manage to carry off the callowness of youth. According to the director, the actors recorded much of their dialogue while in the studio together, an uncommon practice in modern animation, where voice actors rarely work in the same room. It suggests a real rapport, one that’s palpable on screen, even playing monsters.

It may be children’s terror that powers the movie’s fictional universe, but it’s the energy of its stars that lights up “Monsters University.”


G. At area theaters. Contains brief, mild spookiness. 103 minutes.