I made a lego guy suit for Halloween along with my sister and her friend. We searched online for ideas how to make the head and combined some ideas from different sites including coolest-homemade-costumes.com. This was VERY messy to do, but fun and we loved the results.

(me on the far left, my sister in the middle and her friend on the right)
It was fun to work with them on this project because neither of them had ever done much crafting before and they were really happy and proud to see what they had been able to do by the end of it
-The Making Of-
The heads were the most work. The "stud" on top of the head, the neck and the top and bottom of the head were made out of carved styrofoam. We cut it with knives, then sanded the styrofoam. Then we covered it with drywall putty and let it dry. Then we sanded the dry wall putty for a smooth finish. We painted the pieces with yellow paint.

(My sister and her friend cutting out the top head pieces)

(After drywall putty. The one with the hole is obviously the one that goes over your head, the one without the hole is the top piece)

(Me sanding the pieces. Cutting and sanding styrofoam and then sanding drywall was the messiest part as you can imagine...)
The hands were made similar. We cut the hands out of styrofoam, sanded and drywall puttied them, then sanded again. We painted and sprayed them and then stuck the shaped piece into pieces of a large cardboard mailing tube which had been painted yellow as well.
The base and top of the head was held together with wooden skewer sticks, and we covered the space with bristol board (glue gunned it together) and then we painted the whole thing. We sprayed a semi gloss shine spray on top of all the pieces for a nice shiny look. Unfortunately after painting my head turned bumpy/wrinkly so I used stuffing inside the head to smooth it out some

(Which made it hotter and hard to hear.. lol)
The body and legs were far easier. We used cardboard for it all, except the "bump" which had the front section made of bristol board and stuffed with stuffing to hold the shape. I just measured out sizes and cut the pieces of cardboard, using scored lines to be able to glue the pieces together. I didn't take many pictures of this because it was pretty basic.
Then we painted and sprayed these pieces. To hold the pieces together we used velcro strips. There was velcro that held the neck to the body, the head to the neck, the body to the bump (although this was really just one strip, not detachable.. ) and then the legs to the bump (obviously needed to be detachable to get the suit on).
We finished off the costume by printing the lego logo and gluing it to the back.

Let me know what you guys think

We were very pleased with them, although they were pretty awkward to try to see out of, and move quickly in, hahah.
And just to point out- uncountable amount of burns from the glue gun occurred during the making of this project, haha.