Singers are known for the diva-like demands, but find out who's making some unbelievably odd requests.
Queen guitarist Brian May has told the BBC that Freddie Mercury will "appear" on stage during a special performance of West End musical We Will Rock You.
However, he stressed that the new effect was not a hologram. He termed it "an optical illusion of sorts".
We explore this increasing trend of keeping the memory of legendary artists alive in this gallery.