Oh wait, are you playing the zero-duration animation in a loop?
I guess it doesn't raise the Complete event in that case. It's kind of a strange case. For looping animations, Complete is raised every time the animation loops. But since it's zero duration, it's perpetually in some sort of limbo state where it's always but never within the animation duration? Should Complete be raised every update in that case? If an animation loops more than once in a frame, should Complete be raised multiple times that frame?
I'll bring this up with Nate. This actually affects all runtimes.
For now, if you play that animation with loop = false, it should have the same effect animation-wise. but Complete will be raised.