Possible Clues:

• Wet blanket
• Social killjoy
• *Killjoy
• Killjoy
• Portray pope, possibly, as a killjoy
• One who makes everyone get down on the dance floor?
• One who's no fun at all
• Low-down on MoMA perhaps protected by a spoiler
• Gala's killjoy
• Poor type for mixing after introductions to people at receptions?