The melody comes from McDonald's I'm Lovin' It campaign, launched worldwide in 2003 as the brand's long-running slogan and advertising sound. Its five-note ba da ba ba ba hook was designed to be short, catchy and easy to remember, and it has stayed in adverts for more than two decades. Online, creators lifted the sting from commercials and turned it into a meme cue for anything related to burgers, fries, cravings or cheeky indulgence, which is why a three-second clip still instantly signals fast food without a single word of explanation.