30 Days of Doctor Who: Question 27: Favourite special.
Time Crash. It isn't one of hte long Christmas Specials, it's the Children in Need 2007 Special, less than eight minutes long, packed with humour, irony, character, and theme. Complete with the frowny face, time paradox, universal emergency, a decorative vegetable, wibbly-wobbliness, and the brainy specs.

Steven Moffat at his best. If you want to see it, click on the picture.