TTR / LWT: Casting and Contrariness (drabble)

"It's very good of you to take a look at our storybook," said Izzy. "Some
of its casting decisions have been, well, dubious lately."
The Librarian licked his finger, turned over a few pages, rubbed the
paper, and hit the spine of the book a few times with a small bookbinder's
"Ook," he said.
"A trial run? Let's see. I suppose something like this ought to do," said
Izzy, turning over the pages. "Junior Doctor Who And The Brain Of Morbius."
Story Space opened before her, containing Sarah Jane and the Fourth Doctor.
They were dressed as each other.

[ As I was saying, present the Book with something that can only be cast
one way and... ]

John Elliott

Thinks: This is what a nice clean life leads to. Hmm, why did I ever lead one?
-- Bluebottle, in the Goon Show