CLEVELAND — The legend of Mike Napoli was officially born three years ago on Boylston Street.

The Red Sox already had paraded through the city celebrating their World Series victory, but the party never stopped for Napoli.

He hopped bars to be among the people. He was behind the bar pouring drinks for everyone at McGreevy’s. He ran through shirt after shirt — from a plain grey crew to a red Marty Walsh T — until he didn’t have one to wear anymore.

Not that it stopped him.

He stalked the streets shirtless into the night, the portrait of championship revelry.

The lasting image of the three years Napoli spent in Boston is as a man of the people.

“It’s my personality,’’ he said. “I like to have fun. I’m not afraid to get out there on the streets and be with the fans and have a beer with a fan. It’s who I am and who I’ve been my whole career.

Napoli joined the Cleveland Indians this season, and that legend has only grown.

Midway through the season, Napoli spotted a fan, Nate Crowe, at Progressive Field with a sign that captured his spirit in a mere three words.

“Party At Napoli’s.’’

The sign was self-explanatory. The phenomenon it’s become as the Indians get set for their American League Division Series matchup with the Red Sox on Thursday is beyond explanation.

Crowe had the slogan printed on a T-shirt and delivered it to Napoli, then saw Napoli wearing it during a postgame interview after a walkoff win over the Kansas City Royals in June.

From there, it took on a life of its own.

The city of Cleveland rallied behind it as the Cavaliers won an NBA championship that ended a 52-year title drought. The Indians rode the wave all the way to a 94-win season. The Indians worked with baseball apparel company 108stitches to print more shirts. Those shirts flew off the team store’s shelves. In August, Napoli donated $120,000 in proceeds from the shirts to Cleveland Clinic Children’s Hospital and VeloSano, a charity bike ride. In September, Napoli and the Indians hosted an actual party (with Napoli) at Progressive Field’s Corner Bar. For a stretch this season, Napoli had the slogan stamped on the barrel of his bat in place of his signature. (Major League Baseball insisted on being party-poopers, asking him not to use the bats and also asking players to stop wearing the shirts during batting practice.)

The clever sign that caught Napoli’s attention ultimately ended up catching fire.

“It was something, when I saw it, it was cool and we were able to spin it off to a charity thing and it ended up being pretty big,’’ Napoli said.

After being traded from Boston to Texas after the deadline last season, then joining the Rangers for their playoff run, Napoli signed a one-year, $7 million deal with the Indians with the vision that Cleveland was a place he could win. When he got there, he realized the personality that made him a cult-like figure in Boston would eventually became infectious in the Indians clubhouse.

“I like to do things in the community, have fun during the year, try to do different things that include fans,’’ said Napoli, who had career highs of 34 home runs and 101 RBIs this season. “It just happens to work out that way. I can’t really explain it. I guess it’s just my personality. Come here and try to bring everyone together to have fun and have a good year.’’

Around the Indians clubhouse, everything about Napoli was as advertised from the start.

“Believe it or not, he is the party,’’ outfielder Rajai Davis said, grinning wide and nodding his head. “That is him. That’s just him.’’

“The guy’s a stud, man,’’ said closer Cody Allen. “Not only on the field, but I’ll tell you what, he’s one of those guys that you could be from anywhere in the world, you could have different beliefs, whatever your background is, you’re going to get along with that guy. He’s going to push you, he’s going to make you better. He keeps everything moving in the right direction. He’s a big part of our culture change in the clubhouse.

“We had a lot of really good guys in this clubhouse already, we’ve had a core group of guys here for a few years now that have done an unbelievable job, but him bringing his experience from different winning organizations and just kind of adding onto that, it’s been a blessing for us to have him.’’

Watching Napoli day in, day out, Davis learned as much about the euphoric Napoli that took Boylston viral as he did about the one with a reputation for his relentless work ethic.

For seven of the past nine years, Napoli has been in the postseason. He’s a .248 postseason hitter with seven homers and 27 RBIs.

“He’s that kind of player,’’ Davis said. “When you’ve been in the playoffs, I don’t know, 10-something years in a row . . . that’s the kind of player you are. You’re a postseason player. You’ve got that label. That’s what he is, so a lot of guys lean on him.’’

The Indians have hopes of partying the way Napoli did in 2013.

Davis acknowledged he might not be able to take it to Napoli’s level.

“The odds are probably 1 and 2 billion,’’ Davis said, laughing. “But I don’t know. I’ve never been in that situation before.’’

When Allen thought about it, though, he saw the party for what it was the entire time.

“Honestly, I think this is actually Napoli’s house,’’ Allen said, opening his arms and looking around the clubhouse. “And I think the party’s here.’’

Julian Benbow can be reached at jbenbow@globe.com. Follow him on Twitter @julianbenbow.