Beep woop whirr boop.
I was first trying to build the sphere. One beach ball and paper mache was the first idea. It will turn out that this was a horrible idea. The surface did not have enough tension and it was nearly impossible to spread the paper uniform. To make it more stable, pebbledash was used. For the head, I used two styrofoam ball. Why two? Because paint color corroded one, that's why.
The result was already cool but it would be cooler if he can move around. Hence, I was wiring some cables together to make it happen. This worked fine, the programming was fast and the motors did what I wanted. Nevertheless, I decided to build a new and better system (mainly because the paper mache deformed after a while). The result was a big styrofoam ball as body and using a wood tower for the internal construction.
The end of the story is that I needed a lot of time to build this (actually, I reworked things so many times that I build the robot at least two times in different versions). However, it was a fun project and all things considered, I still think that this was a cool idea.