I'm unclear as to why you find it odd, especially since the things you've been reading have said it is normal to develop imaginary friends beween 3-5 years old. December is only a few months away. It makes total sense if your kido is starting to be big on pretend. Yeah, a little early, but definitely seems within the range of normal to me. By the way, I had my childhood imaginary friends for a very long time, and probably started a bit early as well. Mine had really funny names like "Bookie" and "Mattress" and "Stampy."
I'm pro-adoption reform, but not anti-adoption.