I quite fancy a commentary of that Jack/Ten story that involved unicorns, it was so beautifully mad! Failing that I'd take one during 'Rhyme and Refrain.'

Of course now I'm wondering about all the ways to do this. Perhaps by stalking the fic characters like David Attenborough, and explaining your motives, or alternatively just voice-overing everything (or appearing inside televisions and radios,) hence making everyone in the story feel like Sam Tyler.