I have no idea what caused the strange appearance, but it doesn't seem to bother the bird at all. It flies normally, perches in the trees, and sips nectar from the feeder and the flowers. It also engages in some typical hummingbird aggression.
No doubt there are as many variations in birds within the realm of "normal" as there are variations in humans. That's one of the things that makes backyard birding so interesting.