A few minutes after Supervisor Cleaves had been revealed to be a "Doppelganger", and had run out of the room screaming and howling, Buzzer came to the Doctor with a very worried look on his face.
"Doc," he said, "er….um…."
The Doctor had been talking quietly to Amy, trying to soothe her somewhat rattled nerves, but he turned to Buzzer encouragingly. "Yes, what is it?"
"Well, Doctor, I was wondering if there was any chance that, well… I might be my own 'ganger and not even know it?"
The Doctor shook his head. "No, not much chance of that. Cleaves – or the duplicate Cleaves – knew what she was, but was repressing the knowledge. I just made it impossible for her to keep pretending any more." Cleaves had only been revealed as a 'ganger when she was unable to feel a hot plate the Doctor handed to her, due to her pain nerves not yet having formed properly.
"Still," the Doctor continued, "if you are worried about it…"
"Oh yes," said Buzzer, "I am."
"All right. Give me your hand for a moment," said the Doctor, producing his sonic screwdriver, the trusty gadget that had got him out of uncountable awkward situations.
Buzzer extended his hand to the Doctor, who grabbed it, switched on the sonic screwdriver, and applied the device rather brutally to the centre of Buzzer's palm.
Buzzer yelled and leapt away from the Doctor, waving his hand around in agony. "YEEEEEEEEEOWWW! Shit! What did you do that for, you daft git?"
"Well," the Doctor said mildly, "there's nothing wrong with your nerve endings, is there? So you're not a Doppelganger!"
Amy doubled up with laughter and was soon followed by Billy and the others, although it was quite a while before Buzzer himself saw the funny side of it.