Spinning wheels beneath walk surface

When fighting mobs on catwalks and places where you can see past the walk surface, I will occasionally see these strange structures hanging out below the walk surface. They look like wheels spinning and they seem to be tied to timed effects.

I'm talking about the shapes indicated by the yellow arrows in the screenshots below.

WTF are these things? Are these supposed to be in production code?

I managed to grab some screenshots running with a friend using Sunder with stun tricked out.




I also started a DOT archer using poison and bleeding and got some screenshots on the wooden bridge in the Submerged Passage.