"Hmmm," William agreed noncommittally. He didn't know how to ask whether Pete felt as if he'd involuntarily orgasmed his not-quite-Patronus into existence without inviting awkward questions.
"They are corporeal, aren't they?" he asked instead. His mongoose and Pete's lion were in the middle of a mysterious nose-touching, whisker-twitching ritual and appeared to be getting quite chummy. "I haven't..."
As if hearing its cue, the mongoose twisted around and ran back to him, leaping up into his arms where he just barely managed to catch it in time. He made a little 'oof' noise of surprise and subjected himself to a round of investigatory sniffing. Well, that answered that.
"I don't know what they are," he told Pete honestly. "But I think they were created from us somehow. Otherwise it seems a bit too coincidental."