"One of the coolest moments of 2020 was when Usain started following me on Instagram and we had a little chat in the DMs (Direct Messages), that was big for me," the 24-year-old says, chatting live with Olympic Channel's Ash Tulloch.
The Norwegian hurdler was delighted too see Bolt pop up in his follows.
"To be honest, I'm one of the biggest fans of Usain, growing up, seeing Usain run, I'm a huge fan and I will be a fan forever."
The one he set at the Impossible Games, running the fastest 300m hurdles in history is a case in point.
"I think no one in track and field will be able to fill his shoes. But I don't think that's what it's about, he gave us the arenas, he opened new doors.
"He opened a new playground and it's just for us to have fun there... I just try to follow in his footsteps, but it's very, very big shoes to fill and and I don't even want to go that way, but I'm I'm going to use him as an inspiration."
Bolt may have retired from athletics, but Warholm says that the sport is still close to his heart.
"It seems like he's also like a guy that wants other people to succeed... I think he wants our sport to keep moving forward."
Read on to see what this Norwegian sensation has to say about that world record he's come so close to breaking, visiting the King of Norway in his shorts, how he's stayed motivated, and why he needs a new apartment (Spoiler: It has a lot to do with Lego).
And you can watch the full interview right here:
Karsten Warholm on world record: 'I'm closer than anyone'
So does that number keep him up at night, does he have it written on his wall as motivation?
"No, no, I don't need to because a journalist confronts me with that question every time. So I'm reminded once a week at least," he says laughing.
"I try to think that that it's better than having the third fastest time," he laughs again, "so, you know, always trying to keep a positive mind."
But for someone who runs this fast with those big powerful strides, he isn't in a rush.
"I know where we're going," he says.
"Right now, if you look at the numbers I'm one tenth of a second from from making that time. I'm closer than anyone has ever been before.
"But still, Kevin Young is better than me and it's nice for me to have that to work towards, especially in this Olympic year. We need motivation right now, and I'm going to work towards it.
"What I'm really happy about, I started training with Leif (Olav Alnes - his coach) in 2015 and that was the first time I ran the 400m hurdles.
"And every year since that I've had improvement. I've been better every year. And if I can improve one more year. Yeah, you can figure it out yourself!"
Has Warholm broken the world record already?
The question is, has Karsten already done it in training but hasn't told us yet?
"No, no, no, no, no, no..." he asserts. At least six times.
"I tend to be at my best in competitions. It's not often that I run faster at practice than I do in competition. Because if I did, I would have to find a new way to work, I think, because it's only at competition that you get measured.
"I'm just lucky that we are able to sit here talking about an historic time and a world record, I think that this is a good place to be."
Karsten Warholm Tokyo 2020
With the rescheduled Tokyo 2020 Olympic Games coming up this year, how is Karsten feeling?
"That, of course, helps me a lot.
"I didn't feel like I was able to compete as much as I wanted in 2020, and I'm hoping that the summer of '21 will give me more chances to run for better times.
"But also to run against all my competitors and for my competitors to be able to train normally again, for the world to become more normal again and just show everybody how how hard I've been working.
"That is my motivation and hopefully show the world that I'm still fast."
Karsten Warholm's Lego jedi
While Warholm has been lucky to be able to keep training in Norway while many athletes around the world have been locked down and kept away from training facilities due to the spread of the coronavirus, he does miss certain things.
"So I'm a social person and I like spending time with my friends, but there's not been a lot of that the last year.
"So I'm hoping that someday, very soon, I will be able to travel again, be with my friends and just enjoy going to the cinema.
"But I found new hobbies. Right now, my number one thing is to build Lego. I've been doing that for one year now and and now I need a bigger apartment because it's Legos everywhere right now!"
Warholm has built the Disney Castle, Manchester United's stadium Old Trafford, the Tower of London, he's a black belt in Lego.
"But for now, my life is quite boring. It's mostly training and relaxing, watching TV. Of course, I love my TV as well."
To get to where Walholm is you have to sacrifice, but he prefers to see it as prioritising.
"It's funny because a lot of people look at my life and think it's really super cool and everything and sometimes it is, of course, but most of the time I got to keep my mind on doing the right decisions.
"So when somebody asks me if I want to climb a mountain, I got to say no because I can get injured. If somebody asks me to go skiing, I can't go skiing because I'm afraid to get an injury. So all those things I got to keep in the back of my head."
Before he moved to Oslo to train with his coach Leif Olav Alnes, Warholm led a normal teenage life, but he's had to give up two of his favourite things.
"I'm a huge fan of candy and before I drank a lot of beer. But now it's all about the good stuff. I just eat salads and lean meat and all those things."
Karsten Warholm coach
Together they light it up on the track and are heavy on the lols off it.
Warholm and coach combine for some funny and creative social media posts, and their relationship runs deep.
"It is very special," Warholm agrees.
"And I think people tend to forget how important it is with coaches and people who know what they are doing and have the right values and and also know how to see you as a human being, because sometimes we just need that, right?
"I don't think any top athletes are robots, everybody's human. So we communicate very well. And that is probably the best thing about our relationship. We speak the same language and we are on the same frequency.
"So often, when he gives me something that I need to do better, I understand what he means and vice versa. So I feel like me and Leif we work really well together.
"And I hope that we can do that for many, many years."
So what's one piece of advice that stands out?
"He actually just says to me, Karsten go out and enjoy and whatever happens, we will deal with it. You know, he always says, plan for success and handle failure. And I think it's a good one."
Warholm is a huge star in Norway, at the World Championships in Doha 1.5 million people tuned in to watch him win the 400m hurdles live on Day 4 of the 2019 Worlds, "and we are only 5 million people," says Karsten. "So that is like over 25% watching it live. It’s crazy numbers."
Now his coach is getting just as famous and they've just done a national TV show together - a 5-part series that Warholm and his coach did for Norwegian national broadcaster NRK, showing how they live and work.
"We've had some requests and doing TV shows before," he says, "but we didn't have time because we wanted to put all our time into into performing even better.
"But when this awful coronavirus came into the world and everything was shut down, we had some spare time to let our camera team into our training and take a closer look at what we do.
"And I think what we do is somehow unique. So I wanted to show people how we work and how me and my coach communicate to get the results that we have.
"So I think a lot of people actually like the TV series, the first episode actually, we visited the king of Norway at his castle. So it was very interesting.
"And it was a journey. And I felt like it was a very nice way to spend the lockdown, showing how we trained and worked hard to perform."
The time Warholm wore shorts to meet the King
As part of the Norwegian TV series, athlete and coach met King Harald of Norway at the royal farm in Bygdøy over the summer.
Social media filled with comments when the star hurdler showed up in a pair of shorts.
“You are lucky you can use shorts in this heat," laughed the king.
King Harald spoke with Karsten and Leif about sport, the royal is an three-time Olympian and as an accomplished sailor in his day won World Cup medals.
His father, King Olav, won Olympic gold in sailing 92 years ago, and King Harald told Warholm that his biggest regret was not winning an Olympic medal, that his career felt incomplete without it.
King Harald even carried the Norwegian flag at the Tokyo 1964 Olympics - the last time Japan hosted the Games.
He had one piece of advice for Warholm:
"Do not carry the flag," the king said, "if you compete the next day."
"It's not wise. It's a long day if you want to have the flag. It was fun to do it. It was the first time and it's an honour. But we were to compete the next day, so it was not wise," he explains.
"So the king forgives me if I say no?" asks Warholm.
"I forgive you, because I'm pretty sure you'll be asked. There are some who will run 1500 meters... so they can get the flag," the 83-year-old monarch laughs.
Addicted to winning
Now that Warholm has a royal pardon from being his country's flagbearer in Tokyo, he can focus 100% on what so many now expect from him:
A gold medal at the Tokyo Games.
But like most high achievers, the pressure from the outside is nothing compared to his own expectations from within.
"A lot of things changed after I won the World Championships, everything was crazy," he says.
"It wasn't that normal for Norway to win in athletics and I felt like people really appreciated what I had done and it changed everything.
"And from that point forward, you also get used to winning, right. So you want to win again. From that point, you can probably say that it was some kind of addiction, actually, because I wanted to be at the top again.
"I wanted to continue performing and continue being one of the best in the world. That's the pursuit I'm still on and it motivates me every day."
When the 400m hurdles rolls around at Tokyo 2020 expect Warholm to be ready as an entire nation tunes in and holds their breath for 42 seconds.