It’s been eleven years since Disney-Pixar’s “Monsters, Inc.” first showed us what those monsters hiding in our closet are really up to. And it’ll be another six months before the prequel, “Monsters University,” arrives in theaters. But in the meantime, you can whet your monstrous appetite in a whole new dimension as “Monsters, Inc. 3D” opens wide this weekend. We all know it’ll be good to hang again with Sulley (John Goodman) and Mike (Billy Crystal), but here are Five Film Facts about “Monsters, Inc. 3D” you may not know.

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1. Boo Yah

Mary Gibbs was just 2 ½ years-old when she provided the pitch-perfect vocal stylings of Boo, the adorable little girl who terrifies the entire monster kingdom when she mistakenly makes her way to the Scare factory, Monsters, Inc. Gibbs -- the daughter of one of the story artists on the film -- nailed the part, but getting such voice-over gold was anything but easy. Instead of situating the youngster into a sound booth, the technicians were forced to follow her around with microphones while she played. “Mary was too young to understand what we wanted her to do, so we had to trick her into stuff by playing games, jumping and running around, talking to puppets.... Later I used the same tricks working with Ed Asner,” director Pete Docter recently wrote during a reddit AMA. Gibbs’ only other credit since “Monsters, Inc.” is for vocal work in the video “Mulan II” (2004). She doesn’t yet appear in the “Monster’s University” credits, and since the prequel takes place before the action in “Monsters, Inc.” it’s probably safe to say she won’t.

[Related: Get local tickets and showtimes for 'Monsters Inc. 3D']

One Great Trailer

2. In a way, the re-release of “Monsters, Inc.” is just one long trailer. With four Academy Award nominations, one win for Randy Newman’s Best Original Song, and over 500 million dollars grossed worldwide, it’s no wonder the film is getting a sequel, ahem, a prequel. “Monsters University” tells the origin tale of Sulley and Mike, who apparently didn’t start out as such great friends, as you can see in the trailer above. Fortunately, that’s not reflective of how Goodman and Crystal are off screen. “That’s why I think there’s a lot of affection between Mike and Sulley on the screen -- the relationship between the two of us is so real. We really love working with each other,” Crystal recently told The Hollywood Reporter.

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Monster Buster

3. It’s hard to imagine anyone other than Goodman playing the stud Scarer Sulley, but in fact, he wasn’t the first choice. Apparently, director Docter tested Bill Murray for the role, and wanted to offer him the part. Per Murray’s MO, the filmmakers left messages on the actor’s answering machine, trying to get him to bite. Murray never returned their calls, so they assumed he wasn’t interested. It wouldn’t be the only time the famously difficult-to-get-a-hold-of actor went AWOL, he also pulled the disappearing act when offered parts in “Who Framed Roger Rabbit” (1988) and “Charlie and the Chocolate Factory” (2005).

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Not to Infinity and Beyond

4. Speaking of casting what-if’s, Crystal could have very easily been cast in the first Pixar film, “Toy Story” (1995). In the very early stages of production, Crystal was offered the part of Buzz Lightyear, the spaceman toy, who would famously be voiced by Tim Allen. Crystal turned down the role, and it remains a pain point for him. "It's the only regret I have in the business of something I passed on," Crystal told ABC News.

5. A Whole New Dimension

According to Docter, the animated feature was perfectly suited for a 3D conversion. “For us, the 3D aspect of it is another way to communicate emotionally. It’s a tool that we can use to make the audience feel something. And it takes it to another level,” says Docter in the featurette above. Of course, another great reason to convert the film to 3D is because you get to have a whole new theatrical run as well. Cha-ching.

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