Imaginary friends; imaginary toys

Thomas is obsessed with Percy the Small Engine, and this item never leaves his hand. He wakes up most mornings with the imprint of Percy's wheels in his cheek (other kids have soft lovey toys, but not Thomas).
James has been patient about Thomas's Percy monopoly, but lately Thomas's vocal refusals to share have started to grate. We were near a toy store the other day and I broke with normal practice and offered to buy James an extra Percy. "No, thanks. I have another Percy that's battery-operated; I just don't have the batteries yet. I'd rather have a book, please."
Charmed, I bought him a new book (about art, as usual). At home I asked him where the battery-operated Percy was. "Oh, it's at my repartment. My sisters like to play with it most of the time, but they always let me have a turn when I ask. My sisters are not bad at all about sharing, considering that they are all only one year old."
I'm afraid I made him self-conscious by my delight at this. I totally understand where he's coming from; I had so many imaginary friends as a kid that it was hard to keep up with all of them. (I could still tell you what they're all up to, but I won't.)