Celebrities using stage names is a tale as old as time, but many people plying their trade in Hollywood don't have the privilege of using their real names. When an aspiring star's given moniker is deemed "too hard to pronounce" or "too foreign-sounding," their agent or another industry professional may goad them into picking a more "American" name. First, here are 15 celebs who were pressured into changing their names for Hollywood: 1. Bruno Mars's real name is Peter Gene Hernandez. As a toddler, he earned the nickname "Bruno" because of his resemblance to wrestler Bruno Sammartino. At 17, he moved to LA, where, as he told GQ , people would tell him, "Your last name's Hernandez, maybe you should do this Latin music, this Spanish music.... Enrique's so hot right now." So, he adopted the stage name Mars to prevent being stereotyped. 2. Christina Milian was born Christina Flores. When she first started working as a child actor, she auditioned under her legal name.…