I don't think two people can have the same hallucination at the same time. "Mind Meld" is something that only happens in movies.
That being said, it is possible for two people to REPORT having the same hallucination. They probably influence each other after the event as they discuss what they experienced. This can even happen to a whole crowd of people.
Let's say there is a very close lightning strike which induces the hallucination(s). As I stated in the article about NDE's, people see what they expect to see, so the visions might be similar. For instance, both people might say that they saw heaven. Person A says, "Did you see angels? Person B then agrees that he saw angels, and adds to the story. Person A then agrees to these other details. These two people are not lying; they both believe they are telling the truth. People are very susceptible to suggestion. That is why scientific studies must be designed very carefully to eliminate any possibility of influence which researchers call bias.
Of course, it is also possible that they are lying. Perhaps Person B agrees with Person A because he thinks that it is the polite thing to do. Perhaps Person A is a dominant person, and Person B is submissive. Or perhaps the two are concluding in a hoax.