Possibly, I'm Insane

The year that Athena and Fortuna developed an obsession with ballet (and more specifically the tutus associated with ballet), Rose suggested they should go see The Nutcracker performed.

The Doctor shuddered in deep horror. “Never. It’s horrifying. If you’d seen the real Nutcracker, you would understand.”

“The real Nutcracker?” Rose echoed.

“Yes, there’s a planet reigned over by a nutcracker, and he is terrifying. Always chomping down on people’s bits to punish them.” The Doctor shuddered again. “Where do you think Tchaikovsky got the idea from?”

Rose stared at him. “…You know that’s not what happens in the ballet, right?”