“It has since emerged that there are back up envelopes for every category and Beatty was given the Emma Stone back up envelope by mistake.
Off stage they realized that they still had two best picture envelopes. The Best picture envelope for Moonlight hadn’t been opened.
Executives from Price Waterhouse who tally the Oscar results immediately realized there was a problem when Dunaway read out the name La La Land.
An official tried to get on stage to immediately rectify the mistake.
Just seconds before, confusion was etched across Beatty’s face after he opened the envelope. He could be seen taking a second glace inside the winner’s envelope before handing it over to Dunaway who read out La La Land.
Host Jimmy Kimmel came forward to inform the cast that Moonlight had indeed won, showing the inside of the envelope as proof.
La La Land producer Jordan Horwitz then graciously passed his statue to the Moonlight producers.
‘I knew I would screw this up,’ Kimmel, a first-time host, joked. ‘I promise to never come back.’
Even though it wasn’t strictly speaking Beatty’s fault, he exited the Dolby Theatre through a back exit to avoid press.
The unbelievable mishap came at the end of an otherwise flawless evening, which saw Casey Affleck and Emma Stone take home their first Oscar.”
There was an envelope switcharoo. When the frantic guys with the headsets came out, one of them took the envelope that WB originally handed to the producer(?) who had just finished his speech. Another headset guy handed a 2nd envelope to WB who moved toward the mic for the reveal. Obviously there are duplicate envelopes if Emma Stone was in possession of her winning envelope.
ETA: Cross-posted with doschicos more official explanation.
It is sad that Warren Beatty was put in this position.
I just saw a replay and Warren looked in the envelope a few times. I’m thinking Faye just saw the La La Land part without reading the whole card.
It wasn’t Beatty’s fault.
I always wondered if people ever make mistakes in a big event like this. Now I know 
I didn’t think the evening was flawless. Kimmel was good, but I did not like him making fun of Mahershala Ali’s name.
I’m sure that Faye was getting impatient and thought Warren was just messing around.
I can understand that- they were there to announce the winner (a big honor) and she didn’t know why he was hesitating. She/they should not have had to have any thought whatsoever that they were not given the correct card. Warren Beatty may have thought he could look like an idiot if he refused to declare a winner. Really, they were kind of in a no win situation. And his sister was in the audience. Very sad. Long careers for both presenters , and they will probably always be remembered for this Oscar craziness.
Warren is totally blameless here – he is 79 years old so I am betting he was thinking he was confused. So he handed it it off to Faye thinking she would see the error as well if there was one.
She just didn’t even bother reading the card and saw La La Land and announced it. I think she was embarrassed by Warren’s hesitation or thought he was making a poor attempt at humor.
I really don’t want to blame age, that’s too easily spread, clouding whatever happened. I prefer the SJ Mercury News speculation the, um, White House was behind it…
A lil more, from LA Times http://www.latimes.com/entertainment/la-oscars-2017-89th-academy-awards-how-could-the-best-picture-mix-up-1488175439-htmlstory.html
And on top of all this, you’re hesitating, millions of people are watching, and the show was probably already running long and the producers want things wrapped up. I do think Faye probably was frustrated with Warren’s hesitation ( I think she said something to him like, “you’re impossible”- I’m sure they didn’t want to be seen as two old fogies up there who couldn’t get things right). I hope older stars won’t become more hesitant to become involved in presenting. They both seemed pretty with it and probably would have done fine if the cards hadn’t gotten messed up.
I think Warren handled it beautifully – he insisted on explaining exactly what happened in very plain terms. Basically he said he read the card he was given.
If you go back and watch it carefully though, the guy from LA LA Land who had the Oscar was kind of rude to Warren. He hogged the microphone, snatched the correct card out of his hand and read it when it appeared to me Warren was about to do so.
I’ll cut the guy from La La Land some slack. Wasn’t his fault either and I can’t imagine how awkward, disappointing and frustrating that moment was from him. It’s more than an award. Pride, careers, and with it money, are tied to wins.
I’m sure he (LL Man) was blown away- and furious.
Given the circumstances, I think I’m inclined to give the La La Land guy the benefit of the doubt, as far as rudeness is concerned. What happened was so bizarre and chaotic that the initial responses (from La La Land people, Moonlight people, Kimmel) were all over the place.
Fake news. 
Just woke up this morning to see all transpired…so awkward, but not as much as the Miss Universe pageant last year with the crown being taken off the wrong persons head. At least there was a bunch of them.
I really think Justin Timberlake got screwed with his song not winning, just like Pharrells “happy” a few years back.
You know what would have made Halley Berrys hair look really cool? A really neat head band or hair Decoration that matched her dress.
I picked the wrong time to fall asleep. But then woke up to watch the replays of the chaos. No one has thought that Matt Damon might be behind this ? :-" Jk, but it would play well into his and JKs fake feud.