The tension that had quickly crept in disappears at Donna's answer; it isn't another demon with the same corporation as him. Which was a silly fear, considering how eagerly he was greeted when mistaken for this Doctor. No one gets that excited about seeing a demon.

"We don't really do that kind of thing where I'm from." He doesn't know about Newt's run in with the aliens, but that was Adam's doing, so it probably doesn't count anyway.

There's more he could say, and he hesitates for a second, fussing idly with his sleeve, not sure how much he should reveal. If Donna hangs out with someone who's an alien, though, she probably won't freak out too much. "But I'm not exactly human, either."