Recycling lines
Oh, and can you think of any instances in either series where some cool line was recycled? I am thinking of the Spike I mean John Hart character in Torchwood saying, "Thirsty now," like Bad!Willow saying, "Bored now," though of course TW isn't a Whedon show. Firefly counts, though, or Dollhouse-- anything that connects to Whedon and uses a line recycled from Buffy. (I might go ahead and use the TW line, actually.)