The Doctor Who and the Unearthly Child.

At Slag Heap School, nosy teachers Ian and Barbara have a conflab over pupil Susan. She spends all day listening to modern beat combos on her futuristic "iPod". Ian dubs her "an unearthly child" because she hasn't got an earthly about anything.
They follow her home to Albert Steptoe's junk yard. There they spot an oddly placed blue police box, emitting a peculiar hum. Ian raps on its door, provoking a voice from within.
Ian: knock, knock
Voice: "Who's there?"
Ian: "Doctor."
Voice: "Doctor who?"
Ian: "Oh, hello, Doctor Who. I wonder if we might join you on your adventures."
Barbara: "Yes, we have a pile of marking, but schoolwork be blowed, we want some excitement."
Doctor Who readily agrees, albeit in a sightly crochety way, and the two nosy teachers are whisked away into time and space.

Archivist: Suthers