Mikey told News.com.au that they had a "one night stand" last year: "I can confirm we did have sex, but it was clearly after Natasha and I had agreed with producers that our relationship was over, and Natasha knew we weren't together.
"I actually didn't want this out as it's not the best way to end my time on the show, but it did happen."
But Stacey rejected Mikey's story, telling New Idea: "Nothing happened between Mikey Pembroke and I. No sexual relations. Nothing. I can guarantee that. And I can sit here and swear on anything."
But she also said she "understand[s]" where the rumours came from. "We did share coffee and we did hang out.
"I'm more disappointed at Michael than anyone. If this is how he takes one rumour then he needs a lot of help because honestly there's going to be a lot of rumours going around in life."
New Idea said later that the coffee date was a way for the pair to discuss how to couple-swap on MAFS, but the show's executive producer told them, "It's not happening. It's already a basket case show. It's too mental. We're trying to get some normality back in the show."
Woman's Day have a video of Stacey swearing "on anything and everything that nothing happened between Mikey and I".
According to Stacey, Mikey reached out to her to talk to her about what Michael said about her the night he apparently macked on with Hayley.
"We went and had coffee, it was really nice and then we hung out with Ivan and Aleks, we were all friends and we were all there for each other. I even helped him on Tinder, he was showing me pictures of girls on Tinder and he was like 'Do you think she's hot?' I was kind of like 'What's going on with your wife?'"
She said Mikey wanted her to partner swap, and texted her asking to kiss. She continued: "He is a narcissist and everything he says is wrong, it is so wrong. I have not even spoken to him once on camera so I don't know where this little affair's come from. I was with my partner and if I wasn't with my partner, I was home in Adelaide visiting my children.
"Mikey is not a nice person, he's not. I now have to deal with the backlash that this has caused me. My children don't need to hear these fabricated rumours about me, it's disgusting. If it was true I would stand up and say, 'Yes, I did it because my husband was out cheating on me every weekend so I had every right to just move on,' but I didn't."
Stacey told Kyle and Jackie O that "Mikey looks like my son, there's no way." She continued: "He is not my type."
On the same day, she told Fitzy and Wippa that she turned down a partner swap with Mikey. "[I] turned it down. I'm not that girl. Not a cheater, I don't condone it."
At the very least, Woman's Day had receipts for the texts exchanged between Mikey and Stacey, Mikey writing: "If they let you swap, would u do it?," and "I wanted to kiss u tonight. Don't mean to be forward but some honesty for one can't hurt!"
And New Idea had even more messages between the couple, where the seemingly confirm they spent the night together. "Hey sorry for leaving this morning," Mikey wrote.
Talking to Chrissie, Sam & Browny, Stacey's fake husband Michael said people would have to until next week to see the scandal break on telly. "You're gonna have to wait a whole week and you'll see."
"Mikey saying it happened, Stacey saying it didn't happen, I've made my mind up," he continued. "I'm not going to sit here and throw stones at Stacey, she's a gorgeous girl. That's her job to convince Australia on that one.
"It does seem like something happened, I mean we don't have to be a rocket scientist to work that one out!"
Hayley confirmed the scandal to Mamamia, saying it happened between initial filming and the reunion, reportedly shot in February. "Mikey calls me during the break and goes, 'I feel so bad for you that you've been vilified and I'm actually flying back from Italy' . . . Production actually paid for him to fly back from Italy to attend the reunion so he could confront Stacey."
She also told Kyle & Jackie O that Stacey and another person are "trying to bring Mikey down at the moment and say that, you know, he's a terrible person, that he's got a bad character, that' he's making all this stuff up to stay in the spotlight and to totally defame Stacey". "It's utter bullsh*t. Stacey just can't stand on her own two feet and cop it on the chin and I'm pretty sure that Mikey's going to do a lie detector test to prove that he did get a leg over Stacey."
Ahead of the reunion, Hayley pointed out to the Daily Mail how stark the story is compared to her own cheating scandal. "The whole time [Stacey] was like, 'I am the victim here, I'm the victim!' The only thing she's the victim of is pointing the f**king finger. What a dog.
"I only ever kissed Michael and I'm ready to say it exactly how I see it."
When Natasha, Mikey and Stacey appeared on Kyle and Jackie O, Mikey admitted that he slept with Stacey "four hours after [they] broke up": "We were well over before I slept with Stacey."
Natasha snapped back: "You asked me for dinner that night, That's not true. You're lying.
"I called you the day after I had read those text messages between you and Stacey. You said she tried to come to you but it was you who went to her," she continued.
Stacey denied the relationship on the radio show, before Mikey offered to take a lie detector test. "The lies that come out of [Stacey's] mouth are ridiculous and you'll see by the end of the show . . . I'm more than happy after this show to do a lie detector test on a number of issues."
Then talking to Chrissie, Sam & Browny, Michael seemed to refer to the upcoming scandal: "I don't know, I'm not going to speculate anything but imagine if that was true, imagine a guy that's literally getting been torn apart every single week, for a kissing allegation, changing this whole life, running around and jumping over hoops for this girl, just imagine . . . I've changed everything, I've literally become a saint, you know."
Ahead of the reunion, a source told OK! that, "There are text messages and other evidence that will hint they spent the night together. For example, some contestants saw her clothes left in Mikey's room that night. Stacey can't hide it anymore.
"They got drunk one night and it happened while they were with Aleks Markovic and Ivan Sarakula," the source continued. That certainly explains Ivan's boys' night comments.
"Stacey really doesn't have much to say in her defence. It's as though she's dumbfounded."
Michael apparently "went into himself" at the reunion when the text messages were revealed. "He came into the reunion really cocky and he laughed at the rumours that she slept with Mikey . . . He was devastated because he actually had feelings for Stacey at that time."
Now talking to TV Week, Michael said that he and Stacey had kept up a long-distance relationship between filming and the reunion, with Stacey organising Christmas for his son and hanging out with his mum while he was in Melbourne. "We were moving in. She cancelled her lease and it was all set to go." But that was put to an end after the reunion's revelations: "I knew, in the back of my head, it was true. This was someone I'd fallen in love with; someone I was dead-set going to live with after the show."
Michael said he knew that the pair were texting even before his own scandal with Hayley. "I was like, 'It's a bit weird you're texting him.' I didn't want to come across like I was threatened by Mikey, so I played it down. I guess a big part of me didn't want to know."
Jon also affirmed the rumour to the magazine, saying: "I'm mates with Mikey. He's not a guy who would be like, 'Oh, I slept with that person' if he didn't."
But Stacey has stuck to her denial of the rumour, saying it was made up for an "extra 15 minutes of airtime" for Mikey.
"I did everything for [Michael] . . . I stood by his side even though everyone was telling me to leave him. I was nothing but a loyal partner, yet he had the audacity to judge me on one rumour."
David explained on News.com.au's Not Here to Make Friends podcast that Natasha spilled the gossip at the reunion in a toast. "She goes, 'Thank you everyone for coming, past and present', blah blah blah. Then she goes to Stacey and goes, 'And thank you Stacey for f**king my husband'. And that was round one.
"Mikey gets his phone out and there's a lot of stuff that goes on. He pulls out receipts, pulls out messages, it was very contrived. Everything was very wishy washy. Still to this day . . . I like Mikey and I like Stacey as individuals, but I still don't know who to believe."
Natasha, who announced the affair to everyone over dinner, told The Daily Telegraph she was "pretty pissed off" when she found out about Stacey and Mikey from Aleks. "He ditched me to have sex with another bride! At first, I was totally beside myself and so angry. But my philosophy is not to hold onto any negative energy."
Natasha acknowledged that no one knows for certain what happened, as Stacey continues to deny the allegation: "In a way, I felt that Stacey and Michael made such a mockery of the experiment because in the end you find out they stayed until the end despite knowing they both cheated on each other."
Yahoo Lifestyle have a video of Mikey taking a lie detector test to prove that he was telling the truth about his affair with Stacey. The operator of the test said Mikey was being honest: "It is my opinion that you are in fact being truthful to that issue.
"There was no strong emotional responses indicative of deception to the declaration."
On Sunday, we'll see how this one affected Stacey and Michael's relationship (although we think we know).
Married at First Sight airs on Channel Nine until Sunday. Join us at our Facebook group Pass the Popcorn to gab about all things MAFS.