In September 2014, Pharrell Williams’ Happy was named the most downloaded song of all time in the UK. It has been streamed 500 million times on Spotify alone and has become a staple at weddings, school discos and family parties. The official video has been viewed 956 million times on YouTube.

But speaking at creative conference Brilliant Minds in Stockholm, Williams said he had no idea the track would become so popular. In fact, it was his tenth attempt at creating a song about fictional character Gru falling in love in animated film Despicable Me 2.

Williams said he was asked to write a song about Gru – who was grumpy and unhappy for most of Despicable Me  – falling in love and becoming more cheerful in the film’s sequel. “I didn’t wake up one day and say I know, “I’m going to pick this five letter word,” said Williams, speaking to Spotify founder Daniel Ek at the conference. “Gru was a character who’s always agitated, he’s like this deadpan, Grandpa humour, he’s always in a bad mood. And so the whole of the first film was about him being always in a bad mood, and it was very funny. For the second film they popped this on me like, ‘hey, Gru’s in love and he’s very happy’ and I was like ‘what?'”

“So [the challenge was] how do you make a song for a guy that’s perpetually in a bad mood? Always irritated? And he’s now just fallen in love. Who’s just happy and nothing can bring him down?” said Williams. “These were the questions and nine songs in, they were like ‘this isn’t right, this doesn’t work’, so I’m bummed out … my ego is shot … but we get to the tenth one and at that point I had nothing else.”

Williams created another song – his tenth attempt – and sent it off to Meladandri and the team. They were sceptical at first – “they didnt think it was right,” he said but Williams asked Meladandri to listen to it a few times before making up his mind.

“When I do a song, if my wife is there at the studio with me, we’ll leave and then we’ll listen to it one time when we’re out. So we listened to [Happy] and we ended up driving round for an hour and a half [listening to it] and we were like, I don’t know what this is, but it feels good,” he said.

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