Caleb Johnson’s review published on Letterboxd:
It's charming, cute, and wholesome as all hell, and that's something all of us need to see every now and then. That's really the selling point of this film, and I knew even from the trailer that I was in for something genuinely heartfelt and sweet.
But what surprised me was just how absolutely mind-blowing the stop-motion in this is. Most of the film is filled with scenes of Marcel, (and other shell-like creatures) going about their everyday hobbies, tasks, and jobs. At first it's something kind of little, like the first shot of the film being a tennis ball seemingly becoming sentient and beginning to roll around the floor. It's impressive, and you think "Huh! That's kind of an interesting shot, I wonder how they pulled that off." Then you watch the rest of the film, and you see so many things happening that you can't even begin to fathom.
There are shots of Marcel falling onto objects and launching other objects, all with the force and momentum of a fucking brick in a single shot and I still can't figure out how they did it for the life of me. Then there are the more subtle, yet equally mind-blowing, shots. An example of this is a shot where Marcel closes the blinds and turns to talk to the camera. Marcel is still shifting and talking and moving around, and right next to him the blinds are still continuously swinging without stopping or cutting away. My dumb little caveman brain has such a hard time figuring out how they were able to pull ANY of this off, and still make it all look as incredible as it does.
That's really the highlight of the film; the animation alone is worth the ticket price, and I guarantee you that it will easily be one of the most fascinating things you'll see in a film all year. Aside from that, the wonderful stop-motion is accompanied by a delightful and sweet story that really ties the whole thing together. Granted, the story's nothing new and nothing we haven't seen before, but it's more than enough to tug on your heart strings a bit.
So all of this is to say: it's time to get YOUR shoes on, (don't be mad, I'm not paid to write these so I don't care) and go see this if you can. You have my guarantee that it'll make your day better.