PHILADELPHIA — Thursday night, less than 24 hours before the Boston Celtics tipped off Game 3 against the Philadelphia 76ers, a waiter recognized SB Nation’s Noa Dalzell. He was a Scuituate, Mass., native who now makes it his mission to represent Celtics faithful in the trenches of 76ers country.

At the tail end of Game 4 — a Boston blowout — two Celtics fans came careening down the loge-area steps.

“John! John Karalis! Locked On Celtics! We listen every day!”

Karalis — the a Boston Sports Journal Hall of Famer — got out of his seat to greet the two fans, decked head to toe in green, as the final buzzer sounded.

Celtics fans are everywhere.

And as Payton Pritchard, Jayson Tatum, and Jaylen Brown slowly dismantled the Joel Embiid-led Sixers on Sunday night, that was painstakingly obvious.

“It never gets old,” Jordan Walsh told BostonSportsJournal.com.

“It’s great,” he said. “It’s a testament to, kind of, the culture that we have, but also, the fan culture that we have here. It’s pretty cool to see.”

Words don’t do Sunday night’s scene justice. But maybe songs do.

Justin Bieber and Vanessa Carlton took center stage late in the fourth quarter. The Sixers’ in-arena entertainment decided to run a karaoke promotion, panning to fans singing Bieber’s “Baby” and Carlton’s “A Thousand Miles.”

The Celtics were up by nearly 30 points by then.

Earlier in the game, “Let’s go Celtics” chants broke out. So, the arena crew turned up the volume on Bruno Mars and Rosé’s “APT.,” blasting the song over the loudspeakers.

Even that couldn’t drown out the Celtics fans.

A sea of green flooded Xfinity Mobile Arena on Sunday. Behind Boston’s bench, that’s all there was. As if the blue and red had been flushed out.

Philadelphia is as prideful a sports city as can be. Murals line the streets. Allen Iverson. Julius Irving. Saquon Barkley. Dick Allen. In Game 3, as the Sixers battled late, the roar of Sixers fans could have shaken the Jumbotron.

By the end of Game 4, Celtics fans had fully taken over the building.

“It’s fun. Obviously, when I played in Orlando, when we played Boston, [we’d] get a lot of Boston fans,” Nikola Vucevic told BostonSportsJournal.com. “I think Chicago is pretty similar [to the Celtics]. When I played there, we would get a lot of fans in other cities. We weren’t as good, so we didn’t win as much to always have that feel. But yeah, obviously with Boston, it was expected, I think. 

“It’s just, obviously, a very historic franchise that’s won a lot, so we have fans everywhere, and it’s great to hear. I mean, especially coming here, a city that is very passionate about their sports, that really gets behind them, for us to hear that at the end was pretty great.”

It was just 11 days ago that the Sixers took down the Orlando Magic in the play-in tournament. A rowdy Philadelphia crowd cheered on Tyrese Maxey as their squad earned its spot in the postseason.

We Want Boston! We Want Boston!

Fast forward to Sunday night, and those exact chants were turned against them.

The first time Celtics fans began the chant, Philadelphia’s crowd tried to tune them out. But by the third and fourth iteration, there weren’t enough Sixers fans left in the building to do so.

“I like how our fans are petty, too. Giving them the chants right back,” Walsh said. “I love that. So, yeah, I mean, we knew we had the greatest fans, but now this just [was a] representation of it.”

Walsh was even tempted to join in, but he’ll have to wait for that chance.

“I was [tempted], for sure, but I can’t do that until we win one more,” he said with a smile.

Celtics jerseys waved goodbye to Sixers fans as they slowly walked toward the exits early in the fourth quarter. By the final buzzer, there was more green in the crowd than blue or red.

“It’s just another luxury,” said Tatum. “Being a part of the most winningest franchise in NBA history, the amount of fans that we have, and how well they travel [is] just something I’ve been fortunate enough to experience my entire career. You understand it’s not like that everywhere else. So, it’s great to be a part of.”

The roar of what felt like a Boston home crowd lifted the Celtics through the evening. Momentum was nearly impossible for Philadelphia to capture, as the crowd was almost completely in favor of its opposition.

“It’s great for us,” Brown said. “I think momentum and energy all add up to be able to sway things into your favor or not. So, just being able to have a Celtics fan base that’s great, that travels well, that gives us [that] energy, even when we’re on the road, I think is very helpful.”

Celtics fans are more than a fanbase. They’re the behind-the-bench crowd in Philadelphia during the playoffs. They’re the nuisance that even Bruno Mars and Rosé can’t drown out.

They’re the waiter at a random bar in the heart of Philadelphia on a Thursday night. They’re the two people yelling out to Karalis on media row as the Celtics take a 3-1 series lead.

The Celtics — much like the New England Patriots, Boston Bruins, and Boston Red Sox (gulp) — for many, are a way of life.

Pritchard kick-started the pandemonium on Sunday.

It all began with a hustle play. Pritchard crashed the offensive glass, jumping up to snag Vucevic’s missed corner three and laying it up without ever touching the ground.

From there, all hell broke loose.

A stepback three over the outstretched hand of Andre Drummond. A 30-foot jumper in transition on the Xfinity Mobile Arena logo. A driving, pump-fake pull-up over Dominick Barlow in isolation.

Pritchard couldn’t be stopped.

“It’s great. I mean, obviously, playing against him, he’s done it, and I’ve watched him do it a lot of time,” Vucevic said. “And he’s a hell of a player. His talent to create his own shot, and his shot-making is at an elite level. And especially for a guy [who’s] a bit undersized, to be able to create that much space and be so efficient — and when he gets in that zone, it’s really impressive to see.”

Then, the pièce de résistance.

As the seconds ticked off the first-quarter game clock, the 76ers knew what was about to happen. Vucevic set a screen for Pritchard at half-court, and Embiid immediately switched with Justin Edwards so as not to give him any space to shoot.

But Pritchard was too quick.

He dribbled around Embiid, and with 0.8 seconds left on the clock, threw up a one-legged, pull-up three from 29 feet out.

“That one to end the first quarter, that one-leg shot was crazy,” Vucevic said. “So yeah, he’s done it a couple of times [since] I’ve been here, and it’s always fun to be a part of and watch it. And I think also what it does, he really gives so much energy to the team. So, it’s great.”

Pritchard’s dominance continued throughout the night. Thirteen points by the end of the first quarter. Eighteen by halftime. Thirty-two by the end of the third quarter. And that was all. 

A scoreless fourth wasn’t enough to hide the wreckage Pritchard left in his wake.

“It’s amazing,” Brown said. “Just, the work ethic speaks for itself. When you see someone put in the work behind the scenes, moments like this, they’re all the better. So, big game from Payton, and I look forward to [him] having more big games throughout the playoffs.”

As Pritchard walked off the floor after his on-court, postgame interview, Lou Williams — who rang the Sixers’ pregame bell — called out to him. He stopped, the two shared a moment, and Pritchard smiled.

The conversation wasn’t audible, but with that many buckets shared between two guys, it was undoubtedly one of great respect.

And the buckets aren’t enough for Pritchard.

When he’s on the court, it’s as if the whole world is against Pritchard. In his heart, that’s how he feels. Every dribble, drive, and defensive possession is driven by the unrelenting desire to prove the world wrong.

And when the shots fall, he yells. Sometimes, to the Celtics fans sitting in the loge section. Sometimes, to opposing fans. Sometimes, into the ether.

He’ll stare up into the distant crowd, shouting (likely) obscenities only audible to those next to him. And sometimes, not even them.

“I’m not sure,” Brown said with a smile when asked what Pritchard screams on the court. “But whatever it is, tell him to keep doing it. It’s working.”

But Pritchard also yells at Boston’s bench. Everyone does.

It’s not just Pritchard.

When he makes a shot, he’ll sometimes glance at the Celtics’ sideline. His teammates will be on their feet, whether it’s a first-quarter buzzer-beater or a tough bucket in isolation. He’s not the only one.

Baylor Scheierman threes lead to a quick thumbs-up, followed by whatever trash talk leaves his lips. Luka Garza‘s scores often yield similar results, minus the thumbs-up.

Even when there isn’t time for a staring contest with Ron Harper Jr., Hugo Gonzalez, and the rest of Boston’s bench brigade, they fill the void.

After Walsh and Scheierman corralled three straight offensive rebounds in the first quarter, the whole bench was on its feet. Sam Hauser got hyped, inching toward actually stepping onto the court. Neemias Queta yelled out toward the action. Assistant coach Ross McMains clapped as fellow assistant Craig Luschenat stood up next to him in the second row.

Just like how Celtics fans are willing to travel to — and take over — enemy territory, the team itself has built up a fortress. An unshakeable collective of humans that never wavers.

“I think it’s huge. We say it all the time, it’s different here. And I really do believe that,” Walsh said. “Obviously, I haven’t been nowhere else, but I really do believe it’s different here, just hearing thoughts from other guys who have come and gone. But I think that’s huge. I think that’s a big part of our team camaraderie.”

Joe Mazzulla roams the sideline, screaming when necessary and clapping until his hands go red. DJ MacLeay catapults up from his seat, bellowing out when Boston makes a big play. Sam Cassell is always active. As is Tony Dobbins, in his unique, quiet demeanor.

Yet the frenzy that often takes over Boston’s bench in the middle of games is the polar opposite of the team’s everyday mentality. The chaotic celebrations are complemented by a strategic, forget-the-past approach.

“I think you just see a team that has experience in the playoffs, that’s been there before, that knows what it takes. You see the seriousness, the approach,” Vucevic said of his initial impression of Celtics culture. “And I think, to me, the most important thing [is that], no matter what’s going on, there’s no huge swing of emotions. We won Game 1. Played great. It was [onto the] next game. We lost Game 2, didn’t play as well. OK, what can we do different? Game 3, won. Great. Game 4, we win now, I know it’s still [just] move on to the next one. 

“So, I think just, obviously, the experience they have, just stay in the middle ground, and understanding that there’s always next game. It’s never over. But I think that, even throughout games, when they’d have runs, when things wouldn’t go our way, we just stay calm and don’t overreact, and that’s very important.”

The Celtics want the Celtics to thrive. Every Celtic.

If Walsh is on the bench, he’s living and dying with every Scheierman thumbs-up. If Scheierman is on the bench, he’s doing the same for every Walsh stop on Maxey.

Queta stands up for every Garza offensive rebound. Every Vucevic triple. And they do the same for him.

Boston fans travel far and wide, infecting enemy arenas, and these Celtics have provided a product that speaks for itself. Even in a year when some didn’t see that reality coming.

And perhaps that’s the exact reason Boston has become the unit it is today.

“Everybody wants to see everybody succeed. Everybody wants to see everybody win,” Walsh said. “I think that that’s what’s kind of boosting us to get us to the next steps, especially when everybody thought it was gonna be a gap year. You know what I’m saying? I feel like that was a big component that got us through that.”

Because this season is anything but a gap year.

“Hell no,” Walsh said. “You tell me, you see where we’re at.”