Heye & Partner created the original German version of McDonald's “I'm Lovin' It” campaign.
The campaign began in 2003 after McDonald's selected the “I'm Lovin' It” concept from work developed in Germany. Heye & Partner, an agency based in Unterhaching near Munich, proposed the idea that became the company's first global advertising campaign.
The campaign was unusual because McDonald's adopted a concept originating outside the United States and rolled it out internationally. Its branding included the phrase, the “ba da ba ba ba” vocal hook, and advertising featuring Justin Timberlake. The slogan became one of McDonald's most durable global identity elements.
DDB Worldwide is frequently named in connection with the campaign because it handled important global agency responsibilities after the concept was selected. That does not change the specific answer: Heye & Partner is credited with creating the original German concept.