The line comes from Austin Powers: International Man of Mystery, the 1997 comedy starring Mike Myers as the swinging sixties British spy Austin Powers. Yeah baby became his signature catchphrase across the film and its sequels, The Spy Who Shagged Me in 1999 and Goldmember in 2002, repeated whenever he was pleased, flirtatious, or triumphant. Clips of the phrase circulated on early soundboards, forums, and later social media, where it became shorthand for playful confidence and retro cool. It remains popular because the films are widely quoted and the delivery is instantly recognisable even out of context.