It depends entirely on how much inertia there is on the shaft, in various forms. The example I was told about was a 200MW peltier, constructed such that rotating it backwards implies pushing back against the water. The shaft itself also had some sort of extra equipment on it, but I'm not sure of the details.

Well, when it was connected about 30 degrees out of phase, the entire unit pretty much exploded. It tore out of the concrete base, and was found to have rotated nearly halfway to the "correct" position.

I haven't seen anything nearly that dramatic myself, so I can't be sure how much it's exaggerated. There's probably a report somewhere.

And I love that party trick. There's no direct equivalence in DC transmission, of course, but I've done similar things with voltage-matching in Electrical Age. It always amazes me how much that game ends up reflecting reality.