Actor Jack Nicholson, cheering on the Lakers during the second half of Game Five of the Western Conference semifinals against the Jazz, is one of the basketball groupies, L.A. style.

AP / Mark J. Terrill

The last time the Celtics and Lakers really were a cultural clash?

That was back in 1987, and the teams really were the yin and yang of the NBA back then.

East Coast versus West Coast.

Bird versus Magic.

Back Bay versus Rodeo Drive.

All of the obvious things.

But it was more than that.

The Celtics were a throwback to the NBA’s past then, from the old Boston Garden, where the rats ran around like they owned the place, to their black sneakers, to the old organ music, to the banners that hung from the rafters like museum pieces.

That’s what the Boston Garden was then, some monument to a lost era that seemed to come right out of film noir, right there on Causeway Street in a part of town where, as one writer once said, “Jimmy Cagney could have very easily tipped his hat to George Raft.”

And the architect of the Celtics then was Red Auerbach, with his trademark cigars and his old-school ways. He was the old patriarch whose roots went back to the early days of the NBA, back when the league had all of the glamour of a tractor pull, and he wrapped himself in the past as if it were some comfortable blanket.

No dancing girls for Red.

The Lakers were the antithesis of all that, playing in what was called The Fabulous Forum, a building that seemed to glow in the dark like a Vegas casino.

They were Showtime in a city that worships at the shrine of entertainment, a city that makes its living selling dreams. La-La Land, where Jack Nicholson sat in the front row, Pat Riley stalked the sidelines as if he were doing an Armani ad, and the Laker Girls seemed to get as many cheers as the players.

Or where else would you walk into a locker room in 1987 and the first two people you saw were Don Johnson, of Miami Vice fame, and Bruce Willis?

Where else could you see Johnson go over to James Worthy and call him “the baddest dude,” or hear Willis tell anyone within earshot that he had once played junior varsity basketball in high school?

Basketball groupies, L.A.. style.

Then again, back 20 years ago, the celebrities were the Lakers’ equivalent of the Celtics’ banners hanging from the rafters, what passed for tradition in a town where a show that lasts for two seasons is considered a longstanding hit. It often seemed that every game back then was like a celebrity peepshow, complete with the owner showing up in a shirt open to the navel with a couple of would-be starlets on his arm.

That was the knock on the Lakers then, that they were forever the boys from some endless summer, chasing that wave disguised as a fast break.

The Celtics were basketball out of some musty old textbook. The Lakers were a highlight film.

The Celtics were tough and gritty. Scratch beneath the Lakers’ surface, and you find only more surface.

The Celtics were hot dogs and peanut shells on the messy old Garden floor. The Lakers’ team picture was taken on the back of a boat, and you could buy frozen cocktails in the Forum lobby.

That was the perception, anyway. And it all came gift-wrapped in the puzzle that’s race in America.

No matter that the Celtics were the first team in NBA history to start five black players, the first to have an African-American coach. Twenty years ago, they had become, in many ways, white America’s team. That, too, was the perception, the fundamental Celtics against the playground Lakers. True or not, it added a powerful element to the passion play that was the Celtics and Lakers back then.

Is it any wonder that Riley resented all of that 20 years ago, felt that all of the stereotypes diminished his team’s accomplishments?

“I guess I’d just like to see more attention paid to the team and less to the entourage that surrounds it,” Riley said back then. “To make a distinction between the team and the marketing of the team.”

For Riley knew that this was the baggage that always came with the Lakers then, no matter how good they were or how well they played. That it was an accident of geography.

Well, Riley doesn’t have to worry now, even if he has been gone from the Lakers since 1990.

Now it’s all Showtime.

The Lakers. The Celtics.

The entire NBA, as if all the marketing directors went to the same seminar.

The Celtics may now play in a building that’s referred to as the Garden, but it may as well as be on the far side of the moon as to how different it was to the old Garden. Cheerleaders. Pyrotechnics. JumboTron. Nonstop music during timeouts. Tom Brady and Bill Belichick in the first row. Basketball game as party.

They don’t even wear black sneakers anymore.

This is the NBA in the new millennium, Boston no different than L.A.. Nothing ever stays the same, not even professional basketball. The names are Kobe and Kevin Garnett now, Lamar Odom and Paul Pierce.

Which is not to minimize these NBA Finals. This is the 11th finals in which these two franchises have met, and that goes back to the ’60s. In this sense, they are linked in ways that other NBA teams are not, and this matchup resurrects all of the history, lets the past run around like a fast break. That’s the wonderful thing.

But a cultural clash?

Not the way it used to be.

But the “Beat L.A.!” chants will still reverberate around the Garden tonight, the same ones that used to ring out in the ’80s.

Some things remain timeless.

breynold@projo.com