17 years after winning an Oscar for "Lose Yourself," Eminem finally showed up to that ceremony to rap that anthem in a performance that was equal parts exciting and bewildering. 

Now, about 48 hours removed from that performance, when it's no longer necessary to keep it a secret, those who were in the know from the start are revealing A.) How they were able to successfully keep it from the public, and B.) How it all ended up coming to fruition. 

As it turns out, this was an idea that dates back about three years. 

"I want to say the first time it was ever talked about was after Justin Timberlake opened with 'Can't Stop the Feeling' in [2017]. There are just these songs when you have an iconic performer opening with an anthem like that it just gets everybody pumped up," said Robert Mills, Senior Vice President of Alternative Series, Specials and Late-Night Programming at ABC, to Entertainment Tonight. "We talked about it with the Academy that Eminem, the fact that he never performed that song and it's such an anthem, and it's one everybody knows and it won the Oscar. Wouldn't it be great to figure out a way to get him to come and do that?"

"It had to be the right time, it had to be in the right place in the show," Mills went on. "This year the producers... had a relationship with Interscope, his label and really made it happened -- and it surprised us up until a few days before because it really was keeping the circle tight so that nobody would ruin it."

Eminem's performance came after a montage showing iconic songs from films past, the final of which was "Lose Yourself." That segued nicely into Em and his band performing live. As Mills put it, secrecy was something that the rapper and the Academy both had in mind in the days leading up to the surprising production. 

"The element of surprise was really paramount to him that I think had it been leaked, he would have backed out," said Mills. "It was great that it was able to be kept such a huge, jaw-dropping surprise."

Mills went on to reveal that only a few select people were in the know all the way up to two days prior to the show. By his recollection it was: The Academy, network, producers, and members of Eminem's team.

Mills also said that Eminem took just one rehearsal prior to going live, and that there were plans in place in case of a slip-up.

"When we did dress rehearsals, there was a whole alternate beat where it was just Eminem's band playing 'You Should Be Dancing' by The Bee Gees with John Travolta in the background," said Mills "so that's how much it was kept a secret and surprise. There was a whole alternate ending to that beat.

"If anybody happened to wander in and see it they would have been like, 'Oh yeah, there's been a switch with a salute to Saturday Night Fever," he confirmed. "It was a fake-out."

As for what was up with the wait, Mills says he didn't know. (However, Eminem has since spoken about that subject).

"I can't say for sure, I think it was really a testament to the producers... who had promised this would be done in the way he would want to do it -- a salute to the number," Mills answered. "He's going to get to perform it on the biggest stage and we'll make sure to keep it secret. There was a real trust factor there."

Eminem won the award for Best Original Song in 2003, but he reportedly took a nap at his home in Detroit instead of attending. 

As he explained in an interview with Variety published on Monday: "Back then, I never even thought that I had a chance to win, and we had just performed 'Lose Yourself' on the Grammys with the Roots a couple of weeks before the Oscars, so we didn’t think it was a good idea. And also, back at that time, the younger me didn’t really feel like a show like that would understand me," he said. "But then when I found out I won, 'That’s crazy!' That to me shows how authentic and real that award is — when you don’t show up and you still win. That makes it very real to me."