I have never done a Lego type thing before and the movie just came out so I thought this would be fun to do. The setup is nothing fancy. It's a very low-res Fume sim that was meshed using a custom piece of geo. It was easy enough to find the dimensions of the lego brick that I needed. I fudged the dimensions a little to make it work, but it was no biggy.
Now, the coloring is kind of the fun part. It's subtle, but I also found the color values of Lego bricks online too, and then using Magma I blended between a dark gray and lighter gray color; using the velocity channel. I first did that with the "fire" bricks, but because of the refraction you lose all of the subtle color difference. I just kept them a single color because it was pointless to do a variation if you can't see it.
Other than that, the ONLY issue I ran into was when I went to mesh the fire and Smoke separately, the voxels overlapped. To fix that I used Magma to test an InMesh of the fire against the Frosted Smoke channel. Then Xmesh'd out the fire so I didn't have to do the calculation and then update the frost mesh.
Oh, and the ground was a meshed plane using different bricks. I did a mesh select > delete to get rid of random squares. Boom.