This was written by the songwriting team of Jeff Barry and Ellie Greenwich, who were looking to recreate the gibberish gold they struck on The Crystals hit "Da Doo Ron Ron." They stumbled upon "Do Doo Ron Ron," but found that creating a nonsense phrase on purpose was not easy, as it had to sound good and sing well. They settled on "Do Wah Diddy," and pictured it as another girl group hit. It was first recorded (as "Do-Wah-Diddy") in 1963 by The Exciters, who were coming off their hit song "Tell Him."
This female version ("There he was, just walking down the street...") topped out at #78, but got the attention of the British group Manfred Mann, who started performing it at their shows. Since The Beatles had some success covering songs by American girl groups (The Shirelles "Boys" and The Marvelettes "Please Mr. Postman"), Manfred Mann decided to give it a shot and recorded "Do-Wah-Diddy," adding their extra Diddy to make it "Do Wah Diddy Diddy."
In the UK, where Manfred Mann was established with the hits "5-4-3-2-1" (#5) and "Hubble Bubble (Toil And Trouble)" (#11), the song topped the chart in July 1964. In America, it took a little longer, but in October they had the #1 hit for two weeks, joining the British Invasion.
The original Exciters version of this song was a rare miss for Jerry Leiber and Mike Stoller, who produced the track. When it tanked, they started working with the song's writers, Jeff Barry and Ellie Greenwich, who were going to record it themselves as The Raindrops. When they started recording it, they got word that Manfred Mann's version was on its way from England, which made their version pointless. At first, Greenwich was put off by her song getting transformed by a male group, but she quickly came around. "We thought, 'With the British Invasion, maybe this is a lucky charm, and it sure was," she said.