As a younger child, I never had imaginary friends, although I was aware of the concept. Instead, I had lots of stuffed animals, with most of them being dogs, that acted as my "imaginary" friends. Each of them had a backstory of how they met me and my other stuffed animals. I'd spend hours playing with them, acting out different social scenarios.
At age 10, I moved across the country, and had to leave all my stuffed animals behind. (My parents offered to let me take just one of them with me, but I declined; I didn't want to separate it from its friends, like I was getting separated from my human friends.) After moving, I "made" an imaginary friend: a boy my age named Nicholas Iverson. He lived five blocks away from me, in a small house, by himself. He had no family, but had lots of pets. He didn't go to school, either, after bribing the local police into not arresting him for truancy. Funny how I always referred to him by his full legal name: not "Nick" or even "Nicholas", but always "Nicholas Iverson".
Come to think of it, I didn't fully believe in Nicholas Iverson's existence, but used him as a mental stim or a fantasy. In other words, his life was like I wished for mine to be. My therapist seemed to like hearing about him. And since I felt pressured to appease her, I kept up his existence longer than I would have otherwise. A year or so later, I told her that Nicholas Iverson moved away to Israel (I'm Jewish), and stopped talking about him.