Rusty introduced the Shadow Proclamation in passing and they sounded really cool but we later found out they just had a room somewhere with an old lady in it. Not so cool. Looked and worked like replacement Sontarans, which made it really fucking weird when they came back for realsies. The Judoon are the ultimate background filler characters. They've only had one canon story, but have appeared whenever the props department doesn't want to make anything new, regardless of the context of the story. (See, The Pandorica Opens)