This one's a bit of a surprise, but it's Harry! The rest of the gang calls him "Mrs. Mop" because he's always complaining about cleanliness on tour.
The Daily Star was filled in by a source: "Harry loves everything to be neat and tidy. He watches to make sure no one drops food anywhere and asked people to leave their shoes at the door and wear slippers." It gets better -- "He went to a supermarket and bought a ton of cleaning products as he didn't think the bus was clean enough. Everyone has their own quirky habits, but we all call him Mrs Mop."
Poor Mrs Mop is just trying to keep things from getting out of hand! Can you imagine how filthy that tour bus could get without Harry's watchful eye?
Photo from MTV