I have a lot of imaginary friends. Sometimes some stay longer than others. But most often it’s the people that I have trouble arguing with in my non-imaginary life.
When a person says something in such a well phrased way that I can’t argue back, but I feel that I don’t agree with, they become an imaginary person in my head. When conflicts occur I usually get so nervous and stressed that I go along and agree. Afterwards I realize that things happened that I might not agree with. This is around the time a mental version of these people form.

Later when I have some thoughts running through my head, these people show up there. And we are, of course, discussing this topic (of my choice). This time, however, I can perfectly articulate myself. I am great at convincing people of my point of view and if they come with reasonable and “clever” arguments back I always have a perfect and smart response.

For a long time it was an ex of mine that was my imaginary friend. Or more: my imaginary opponent that I was trying to get to like me and approve of my ideas. Even looong after our breakup. Recently my imaginary friends show up as people I interact with often (friends, colleagues, etc).
When I get an “aha-experience”, a technically smart friend shows up and I tell ‘em about it. I sound smart and I am the hero of the amazing story.

I have noticed, however, that when I chat with my imaginary friends I get practice in conversation. Very often they are angled discussions, and I have many retakes. But nonetheless I get a chance to vent and to practice getting my thoughts out. Practice makes perfect and this helps in my growth as a person. So I’ll let them stay for now.