"There's a lot no one seems to be able to tell me," he replied, sounding rather annoyed at it at this point. Obviously, he completely understood why, it was just starting to really get on his nerves. At least Donna had avoided the word 'spoilers'.

Her next set of questions simply left him visibly cringing. "I really don't know--to both questions," he responded. "I mean, well, post-regeneration it's normal for me to be a bit off, but it's far too long past that for it to be an excuse. Though, I suppose it wouldn't be the first time I've had a version of myself that was a bit... unstable."

His sixth self was a good example of that, though certainly not the only example.