"Oh. Right, I see." Buffy glanced round, found an empty table, and sat down as she tried to process this. "Yeah, we had a thing like that - this version of Willow who was a vampire turned up from a parallel universe - though that was the result of a spell someone did. Oh, but Angel fell back through from the hell dimension I had to send him through. Never did find out what caused that."
She'd been too busy thanking every deity she could think of to worry about how it had happened.