La La Land, sorry it’s Moonlight: How did the mix-up happen?
The incident happened because of confusion in two envelopes, which was prepared all the time for each category of the Oscars awards.
On Sunday night's Oscars 2017 awards presentation, La La Land was announced as the Best Picture but then had to hand the award over to Moonlight after people up on stage noticed that the envelope containing the name of the winner read "Moonlight".
According to a report in BBC, the blunder happened because of confusion in two envelopes, which was prepared all the time for each category of the Oscars awards.
Two people, who count the votes, already knew who won the Best Picture award in advance. Each has a full set of envelopes containing cards with the winners' names - just in case something happens to the other set.
The report said those people - from accountancy firm PwC - stand on either side of the Oscars stage and hand the envelopes to the award presenters just before they step on stage.
Emma Stone, who won the Best Actress award, had one envelope after she was presented the award, and the other best actress envelope was handed to Warren Beatty, who was presenting the best picture prize, by mistake.
After the incident of the announcing the Best Picture award, Emma Stone had, therefore, said that she was holding her best actress in a leading role card that entire time.
On the stage, veteran actor Warren Beatty opened the envelope, looked at the card, then looked inside the envelope again to see if there was another card inside.
He checked again, then showed the envelope to his co-presenter Faye Dunaway. She read the words: "La La Land."
Following the incident, Beatty explained: "I want to tell you what happened. I opened the envelope, and it said Emma Stone, La La Land. That's why I took such a long look at Faye, and at you [the audience], I wasn't trying to be funny."
Afterward, Oscars host Jimmy Kimmel said: "He was confused because the card, which he showed to me by the way, said 'Emma Stone, La La Land' on it.
"So this was confusing obviously, we thought he was being coy and cute to make everybody suffer but in reality he was perplexed by why her name was on it," he said.
As La La Land crews and cast stand on the stage and acceptance speeches was in full flow, the PwC people and other officials came on stage to inform the film's cast and creators - and the world - that there had been a terrible mistake.