Carl is a square—and we’re not just saying that because the old man’s out of step with the culture at large and still refers to people as dirty hippies. No, Carl is literally a square. He has a big square head, and big square glasses. “At 78, his body resembles a stack of cardboard boxes,” writes film critic Colin Covert of the Minneapolis Star Tribune. He is one seriously boxy dude.
Here’s the thing: Carl’s cube-tacular appearance isn’t an accident. Neither is roly-poly Russell’s round physique. The shape of the characters in Up reflects their personalities. Carl’s square shape symbolizes his steadiness and reluctance to change. “A cube is not something that rolls or moves fast—it is very stable—perfect for Carl,” explains Up’s co-director, Bob Peterson. “A circle can roll and move fast—great for Russell.” We’d say Russell looks more like an egg, which would explain why the kid’s a little off-kilter, but you get the point.
In Up, a character’s shape is the outward expression of his inner makeup. For Carl, “…we were trying to get a physical manifestation of who he was inside,” co-director Pete Docter told The Hollywood Reporter. “We decided he was a closed-off, set-in-his-ways guy, and that felt like a square...Even in the set design, the pictures in his house of Carl are all in square frames, while his wife is in circular frames. You get this really pushed shape language for all the characters in the film.” (Source)
That shape language, as Docter calls it, even extends to Muntz and his madness. Muntz sports a large, diamond shaped head, which PopMatters’ Bill Gibron claims represents the fallen explorer’s “lifelong sense of defeat.” It also reflects the crazy amount of pressure he put upon himself to find Kevin and clear his name. Think about it: What happens when you crush a square? Yep, you get a diamond.