Can multiple people hallucinate the same thing at the same time ?

[Brian37]

Can multiple people see the same thing even though the thing is not real ? I am interested in this because many people have ghost stories and i don't believe in those things , but it's kinda hard to refute it when two people say that they saw the same thing at the same time , lying is always the option , but is there another medical condition that can explain this ?

Hysteria in en mass is basic power of suggestion. So yes and no. It is a delusion ultimately, and you'll believe something bad enough if you want to. 

Here is a prime example of delusional bullshit. No, the sun does not dance in the sky as the conspiratorial morons who pulled this stunt would have you believe. But, just like "miracle" stories today in modern media, people love a good conspiracy story and do not like the mundane real explanations. 

https://en.wikipedia.org/wiki/Miracle_of_the_Sun

It is the same with when people call it a "miracle" when someone survives a passenger jet crash and everyone else dies. I always wonder where the number of dead in a similar crash but opposite result would make it cease to be a miracle. Half and Half? They never want to consider things like weather, pilot error, pilot training, angle of impact, terrain of impact. Nope, if someone survives then all the dead that don't survive get ignored. It is called selection bias and sample rate error. It is gap filling basically. 

There are lots of natural reasons humans do stupid things in groups, or believe crap like a kissing cobra kissing a baby. The handler has sewn the cobra's mouth shut. 

There is a psychology of group think that will cause people in Pentecostal churches to "speak in tongues" and it is flat out mass hysteria and bullshit. 

There used to be a time when there were far more people who would believe that the lady on stage was really sawed in half by the magician, but sane people know today, it is really just an illusion. It is why religion works so well, like the claims of the empty tomb, or claims of walking on water, or healing the blind.  If you want to believe something badly enough, you will. 

Skepticism is the best precaution to insure the minimizing of falling for crap. Humans are not perfect and even the wisest people can be fooled sometimes. But skepticism is a far better safety belt than blindly swallowing.