When Mark Calaway became The Undertaker in 1990, Shawn Michaels was already a Rocker.

At that time, Michaels was an accomplished tag team performer adorned in neon and tassels alongside his partner, Marty Jannetty, about a year away from kicking Jannetty and throwing him through a “barber shop” window and embarking on his own Hall of Fame singles career.

“[Mark] came in and he was already positioned considerably better than I was at the time,” Michaels told ESPN.

Over the next three decades, The Undertaker and “The Heartbreak Kid,” as Michaels would come to be known, would work together to create some of the greatest matches in the history of the WWE. Their harmony in the ring was remarkable. Their relationship outside of it was, for the most part, nonexistent.

“I think in some ways, when we were younger, we were frustrated because we had so much unbelievable natural chemistry in the ring with each other, and had zero of it outside the ring,” Michaels said. “At the time, I was an extremely difficult person. He was less so. There was clearly never any real trouble between the two of us. We just did not care for one another because we were so different. He clearly didn’t like me based on who I was and my reputation. And I didn’t like him based on who he was.”

Much of that had to do with their respective roles behind the scenes: Michaels as the self-acknowledged “difficult” talent and Calaway as the respected voice in the dressing room who kept performers like Michaels in line.

“I never thought of myself as the locker room leader. It just kinda happened, in a sense, just because I was there for everything,” Calaway told “Stone Cold” Steve Austin on The Broken Skull Sessions last year.

That included one infamous moment at WrestleMania 14 in 1998, when Michaels was booked against Austin in the main event, with Mike Tyson as the heavily hyped guest referee. A story in wrestling lore claimed Calaway sat by the entrance ramp taping his fists as Michaels walked out, a visual threat in case Michaels decided not to “do the honors” (to lose) against Austin that night. Michaels has publicly debunked that story, but acknowledged that Calaway made it clear to others that he expected Michaels to follow through with the storyline against Austin.

It took years before Michaels came to appreciate that role of locker room enforcer.

“He never once raised his voice or hit somebody. It bugged me the wrong way. Because he didn’t go and tape his fists. But he didn’t go and make theatrics out of anything. Any time he’d do anything it was very calm, and actually a pleasant conversation. Which was diametrically opposed to the gimmick, so to speak, behind the scenes,” Michaels said. “My immaturity at the time didn’t allow me to grasp that he had it from a respect standpoint. He did it by example. That’s the way it’s supposed to be done. But as I’ve been apologizing for damn near 30 years for everything, I didn’t have the ability to appreciate that when I was younger.”

In 2002, Michaels became a born-again Christian, a turning point in his life and in his personal relationships, including with Calaway.

“When I came back in 2002, he was one of the first guys I went to just to apologize for all of my actions in the past. And he was good with it, but at the same time he made it pretty clear: ‘We’ll see.’ I had a reputation. A lot of people weren’t sure that [my change] was real. Then of course he recognized how [sorry] I very much was,” Michaels said. “When we got to do the WrestleMania stuff, the bond just got thicker and much deeper. We had both changed and grown in a lot of ways. And when we got in the ring, that chemistry was just so dynamic.”

As disjointed as their relationship was outside the ring was as spectacular as their chemistry inside of it. The first classic arrived in 1997 at the “Badd Blood: In Your House” pay-per-view, when Michaels and The Undertaker met in the WWE’s first Hell In A Cell match. “We were scheduled to have probably 30-35 minutes. When we were going out to the curtain, Bruce Prichard looked at us and said we had 55 minutes left. I looked at Mark, and asked him what we were going to do with 55 minutes left. And he said, ‘I’ll walk slow,'” said Michaels, doing a brief Undertaker impression.

Being the first Hell In A Cell match, there was no template yet. Michaels knew that even with all that time to fill, they wouldn’t wear out their welcome. He also knew they needed to do something with the Cell itself: Climb atop it, and then find a way for Michaels to tumble off of it.

“I knew right away when I saw [the Cell] that, ‘My God, I gotta get on top,'” he said with a laugh. “And they would tell me no, because [staying in the ring] is what this whole thing is for. So once we got them convinced to let us up there, Pat Patterson worked with us. Then it was a question of how we were supposed to get down. Because it would look silly crawling down. That was at a time when the tables were sort of getting crashed through in other places. I don’t think we had really done it yet, or at least hadn’t abused it yet.”

Down went Michaels, off the Cell and into the announcers’ table, and a moment was made.

Of course, in WWE, there are moments, and then there are WrestleMania moments.

The Undertaker and Shawn Michaels met twice at WrestleMania, in back-to-back years. The first bout, at WrestleMania 25 in 2009, is considered by many to be one of the greatest matches in wrestling history: a 30-minute classic of brutality, near-falls and eventual exhaustion.

“With WrestleMania, I did what I basically do with people that I trust and know ‘have it,’ so to speak. You’ve got your main points, but everything else you sort of feel, and see where it goes. That’s how that one worked. You’ve got your signposts in the road, you have an idea how to get there, but then you just see how it goes. And we knew we were going to be there for a while,” he said.

The rematch at WrestleMania 26 featured The Undertaker’s WrestleMania streak being put up against Michaels’ in-ring career in a stipulation both hoped would help obscure the fact that they were trying to produce a sequel to a classic.

“That was the biggest concern. It was very much an issue, very much talked about,” Michaels recalled. “I feel like we both felt that the ‘streak vs. career’ stipulation obviously helped. We had at least gotten to the point in our careers where you worry about that topping factor, but you don’t quite apply the pressure to yourself that you did when you were younger. You have to trust in your system, your ability and your opponent. We had some different dynamics to the story. If all of that is fresh, then technically the only thing that’ll be the same are the two guys. You have to do your best to rationalize it, as best you can. Because the big pink elephant in the room is, ‘Can you follow it?'”

The sequel was well received, if not a match that eclipsed the original. Once again, The Undertaker kept the streak alive, defeating Michaels and essentially ending his career.

The Undertaker’s WrestleMania winning streak continued for three more years, but it would end in 2014 against Brock Lesnar. The two men would ultimately share the ring once more, in a 2018 tag team match in Saudi Arabia — Michaels with Triple H, The Undertaker with Kane.

Episode 3 of “Undertaker: The Last Ride” on the WWE Network chronicles that match, which by all accounts was disastrous.

“It sucked from the standpoint of Hunter getting hurt, of it not going well, of it not being received well. All of the negatives that were there,” Calaway said. “When we were in there, you knew the wheels were falling off.”

But Michaels has a different personal take on the match’s legacy.

“None of it bothered me. I went into the whole thing looking at it very selfishly, I guess. For me, it was more about being out there with those guys, and me being there with Hunter, which was something I didn’t get to do near the end. This is a match where I collectively got to experience it with a number of guys that were very significant and very special to me on a personal level, in a certain kind of way,” he said.

“I just have the unique ability where that stuff didn’t bother me. I was more hurt for them. I don’t mean that in a belittling way. It’s just that I figured all of them were going to do another one anyway. There wasn’t finality for them. I look at that match as it stands on its island, alone. I don’t associate it with anything regarding the career of Shawn Michaels. I’m able to compartmentalize that.”

Michaels thinks a lot about finality, about how one is able to close the curtain on a career. It’s one of the reasons he’s appreciated Calaway allowing fans to glimpse the man behind The Undertaker gimmick through “The Last Ride” series.

“No one’s been more protective and more careful and methodical and arguably genius in doing what he’s done with the Undertaker character,” Michaels said. “Especially when people coming through the door would say, ‘Well, that [gimmick] doesn’t have too much mileage in it.’ For it to go all these years … that’s the greatest thing about it.

“I’m glad he got to a place where he’s comfortable about talking about it. He made it special. To pull the curtain back on it means there’s closure coming there, and a lot of people don’t get that.”