The Doctor is chasing after some sort of space baddie—probably daleks, because they're quite iconic and never seem to die. He runs through the streets of London, past such sights as Big Ben and the London Eye—and straight into a crowded convention hall. The daleks trundle through the crowd and out of sight, but in the Doctor's attempts at pursuit, he clumsily runs straight into a group of men.
"Oh, I'm so sorry!" exclaims one of the men, reaching down a hand to help the Doctor up. He accepts it.
"No, no, it was my fault…" the Doctor apologizes, brushing off his trousers and straightening his bowtie. Suddenly his gaze snaps back to the man who helped him up. "I'm sorry, but do I know you? You look familiar." The man has grey, curly hair, and a delightfully long scarf draped around his neck that strikes a chord of resonance within the Doctor. In fact, he thinks as he looks to the men next to the one with the scarf, they all look familiar. Ten of them, in total. There's the one with the scarf, and another wearing a cat pin on the lapel of his patchwork coat, and one man has…is that a recorder? He remembered when he used to play the recorder.
"John Smith," says the scarf-clad man, giving the Doctor a toothy grin as he shakes his hand. "In fact, we're all John Smith," he gestures around to his companions.
The Doctor looks around and finally realizes. He's in the middle of a John Smith convention.