One of the lesser-known features of lucid dreams is the fact that they seem to be contagious to a greater or lesser degree depending on the mentality (neural software) of the person. It has been noted in the literature on lucid dreaming that you are more likely to have a lucid dream after reading about them, or hearing someone talk about them.
I have personal experience of this: when I was 19 I read a book on dreams, the title of which I forget now, and I was particularly interested in the chapter on lucid dreaming. I proceeded to become lucid (conscious that I was dreaming) in at least one dream every night for the next week or so, which was remarkable considering that I only remembered one other lucid dream in my whole life. I emailed a friend to tell her about this, and she emailed me back the next day to tell me that she had dreamed lucidly that night.
I have no suggestions as to the mechanism that might make this contagion possible, except to say that it can't possibly be a biological agent of any kind (my friend was living in a different country at the time).
It's funny - most people report flying or changing things in their environment when they talk about lucid dreams that they have had. Every single time it's happened to me, I've wandered around the dreamscape telling everyone I meet that they don't have to worry, the things that are happening are not serious and terrible, because it's just a dream. Strangely, I have mostly been met with hostility. I say this is strange, because conventional wisdom tells us that the characters in our dreams are figments and facets of ourselves, but in my experience the people I meet in dreams have far more autonomy of expression than I would have expected...maybe this is a lesson to learn about the nature of 'self'.