We own a 10-month-old pug, which up until now didn't show any fear, be it loud noises, other dogs or simply darkness. One brave pup!
Today, while out for a walk late at night, he started to jump and even run away. After a while we realized he is actually afraid of his own shadow. For the rest of the day out, we had to carry him.
An hour later, he was still anxious and carefully observing shadows, jumping and trying to hide from them.
We're not aware of anything bad that has happened to him at all. Just yesterday he was perfectly fine. How we could help him to regain his lost confidence?
EDIT: The extreme fear lasted for about a day. One rough night with him jumping from sleep because something had moved. :) It proved to be impossible for us to do anything. We were ignored.
The following week, however, brought a better experience. Rewards for examining shadows and distracting with toys... well, it kind of worked. He mostly got through it on his own, though.
We realised the biggest issue was, he was not trusting us enough. Working on it. Thanks for your help!