The roar comes from the opening logo of Metro-Goldwyn-Mayer, the Hollywood studio whose lion mascot Leo has appeared before its films since the 1920s. Generations of moviegoers learned to expect a feature presentation the moment the lion opened his mouth inside the circular ribbon. Despite the animal on screen, the recorded roars used for the logo have famously drawn on tiger vocalisations, including Bengal tiger sounds, blended for a fuller and more ferocious tone. That mismatch is part of why the clip survives online as a standalone sound effect.