Kim Kardashian
Kim is just as bad as her husband when it comes to making unreasonable requests backstage. She always asks for nondescript "fruits and veggies," but refuses to eat any that weren't picked that day. Evidently, she just "knows" when they aren't fresh, and she will complain if she suspects that an apple got picked two days before she got to it.
Will Smith
Smith is a notorious Hollywood "cool guy," but his laid back appearance doesn't always reflect what he expects when walking into a dressing room. He once requested a double-decker trailer, just for him, that cost nearly $2.5 million. He even had them install a $200,000 kitchen, and commanded that he got a huge parking space for it every day while shooting.