Just chill. It is totally normal. Dogs can't recognize themselves in a mirror. Just keep the puppy away from it to reduce stress levels.
Your friend probably has Spectrophobia. This is the phobia of your own reflection.
comfort the puppy try to make it feel safe. this lets the puppy know you care and can run to you for safety. if the puppy is scared of an object simply remove it or try to persuade the puppy that it wont harm it. or let it get comfortable around the object if the puppy is scared of things like lightning, thunderstorms, or any other weather hold the puppy, distract it while playing with it, remove it from the area where it scares it the most. If the puppy is scared of you try to be playful or cuddle with it. if the puppy has had an bad and abusive life it may take longer for it to get used to you. Just show the puppy your trust and that you mean no harm.
only if its daylight,some mice could be scared of their own reflection
It is scared
They are not scared. They attack the reflection in the mirror. Male betas are aggressive toward other male betas, so when they see there reflection, they flare up and try to attack the "other fish."
because they are seeing something new
Well, there are a lot of opinions. Some people think that it is bad to carry a puppy because it'll get scared of noise, where as, some people think it is good to carry a puppy because the puppy will enjoy the fresh air.
Not to freak you out, but there may be a ghost in your house. Or your poor little puppy is cared of your bathroom. I wouldn't say that second answer is so far off cause my friends dog is scared of plastic Wal-Mart bags!
I believe you can because the puppy isn't at the stage where it wants to chase or harm the cat. However the cat may feel scared with the puppy.
Cause its scared of the other dog.
They usually keep them between their legs when they're depressed or scared.
Maybe it is scared? Maybe it is trying to tell you there is something scary outside your door?