Sometimes, your current character list can get stale. At times like that, I like to add a new character to the mix. Now, normally adding more doesn't work--for instance, if your chocolate is all clumpy, you don't want to add more chocolate--but characters are a different type of thing. A new character can be bothersome and get the characters out of a rut. They can cause romantic tension, drama, an evil counterpart. They can even be used as a tradeout--add a character, and then take one of the old ones out. (And then there is death, mwahahah.)
So this week, try adding a new character to the mix. Get someone new in there! Are they funny? Serious? Kind? Melancholy? Verbose? Mysterious? Make them interesting. It can get your characters moving again, and moving characters are interesting ones.