For some reason Polymorph triggers Wild Surges when you use the abilities button after the spell has been cast.
A bug I had that required going back to an older save was when I did a "Shift to Natural Form" to become human again and somehow a wild surge triggered giving this ability to Dorn standing next to Neera.
After this he had the button to "Shift to Natural Form" added to his abilities bar and I couldn't get rid of it even with sleeping. To make matters worse when I clicked on it he would get additional uses of "Shift Natural Form" added to his ability bar.
It sound counter-intuitive that Polymorph would trigger Wild Surges when you change shapes, afterall the spell has already been cast - this would avoid strange bugs from cropping up.