Viall, of course, was a contestant on Bristowe's season, joining the show weeks in after previously connecting with her online. The pair made headlines after Bristowe slept with him before fantasy suites, and then ended up getting engaged to Shawn Booth in the finale. However, viewers knew all that. What Viall revealed on Monday's episode was more about his connection with Bristowe before the show. She had sent him a signal on Jimmy Kimmel Live that she was thinking of him, and he had written her emotional love letters before her Bachelorette journey.
"We had never met in person," Viall told host Chris Harrison of his and Bristowe's relationship pre-Bachelorette. "It's one of those things that just kind of escalated quickly, talking and FaceTime, and we talked every day for a period of time. And then she was asked to be the Bachelorette."
Bristowe wasn't immediately offered the gig. The season premiere showed her and Britt Nilsson fighting for the role on night one. The men cast their votes for whom they wanted the Bachelorette to be, and it was Bristowe. "I remember telling Kaitlyn a few times, 'If I'm being totally honest, I hope they pick Britt,'" Viall recalled.
While promoting the season, Bristowe appeared on Jimmy Kimmel Live with Nilsson -- and told Viall to look out for a secret signal meant for him. If she touched her lips with two fingers, that meant she was thinking of him. She subtly did it during the interview.
Then, there were the love letters. "I had told her that I was going to email her while she was filming the show, so I wrote her a bunch of emails with no anticipation of coming on," Viall said.
"I read them. These are passionate, romantic love letters that you emailed to Kaitlyn as she became the Bachelorette and literally started her season," Harrison chimed in.
"What's interesting about that is when we were filming, I think it was at the fantasy suite, because at this point I'm thinking, 'She's going to pick me,' I had mentioned, 'Hey, I wrote you a bunch of emails that when you get back on the grid, you're going to get,'" Viall shared. "Obviously she ended up getting engaged to Shawn, so I just forgot about them. I never read them, I never looked at them.'"
Viall and Bristowe's breakup was brutal, and it took a while for them to get back on good terms. They recently reconnected and appeared on each other's podcasts, where Bristowe mentioned that she "never got those letters." Viall looked through his email and found them.
"I read them, and they were sweet and it reminded me of Kaitlyn and what I thought of Kaitlyn then," he said. "I will say, I'm glad I found them, just because... especially at this point, they are nothing but good memories."
Viall admitted he was "a little bit of a troublemaker" on Bristowe's season, but it came from a good place. "It was sincere," he said.
He was so hurt by Bristowe not giving him her final rose, "I remember wanting to push her in the pool," Viall confessed. But now, with some perspective, he understands. "I don't think we necessarily would have made it as a couple," he told Harrison. "It all works out."
Viall went on to star on his own season of The Bachelor in 2017, though later split with his final pick, Vanessa Grimaldi. Bristowe broke up with Booth in 2018 and is now in a relationship with Bachelorette alum Jason Tartick, who appeared on Becca Kufrin's season.
See more in the video below. The Bachelor: The Greatest Seasons -- Ever! airs Mondays at 8 p.m. ET/PT on ABC.