I was surprised not to see this here already, maybe I missed it.
I got my R4 today and since I love droids I released it from its plastic cage. To my surprise R4 has a retractable third leg and by far the most original way I have seen it. You roll his dome one way to retract the leg and the other way to get it back down.
I'm sorry if this was covered already but I just think this is awesome. I like the clicking sounds because it takes me back. I like the wheels and I really like the retractable leg via dome rotation.