Well, according to Kant via the categorical imperative, since it is imagined, it therefore has ontological reality. So, even if Gabriel the Celt is fictious and created, it is still real.
Why the philosophy? We're not trying to use this as a possible defence at a future criminal trial, are we?
If there is no trial, does that mean there is no crime? How's that for a Zen koan?
I've been reading about Quantum Mechanics, Zen Buddhism and Viktor Frankl's Mans Search For Meaning.
I also saw the documentary "What The Bleap Do We Know?" As a Christian, obviously there's an Ultimate Reality, but there are millions of small or other realities that we (or rather our central nervous system) creates that may or may not be real. I know, I know; it's a strange hobby of mine, but I enjoy this type of philosophizing. But judging by the amount of arguing that goes on here, I'd say we're all philosophers of one type or another.