fun sponge

Someone who makes other people less happy, excited, or enthusiastic about some event, activity, or situation (i.e., someone who sucks up fun from others, like a sponge); a killjoy. A: "We really should be studying for our exams instead of throwing a party, you know." B: "Oh, Marcie, you're such a fun sponge." My husband can be a real fun sponge sometimes, always shooting down all the exciting ideas I suggest for our family vacations. Don't invite Nicole to the party. She's such a fun sponge that she'll probably just sit around complaining the whole time.