A couple of Nichrome heating filaments in the new heater bar that I'm designing hooked up to the new controller I built today began dancing. This is due to the fact that, when heated, they expand along their length. Since they're firmly anchored at each end, they flex away from the channels that they lay in under tension when they're at room temperature, thereby dancing when heated.
I'm going to see if I can find some time tomorrow to explore this with different wire forms. I know that the stress is proportional to heating, and that the heating, aka Joule heating or Ohmic heating, is a feedback effect which will keep going until it either melts the wire, or current is shut off. I think this could lead to some very interesting actuators, especially if I make a brush with a few of these wires together.