John C. Reilly, Jason Segel Shoot Lakers TV Show In L.A., It's 'Showtime'!

Decades after they won their first ring, the Showtime Lakers turnt up at a championship parade in Los Angeles -- and everyone from Kareem Abdul-Jabbar to Magic Johnson was in attendance -- sorta.

John C. Reilly and Jason Segel are starring in an upcoming HBO drama series showcasing the 1980s Showtime Lakers ... and we have video of the actors shooting a scene in L.A.

Reilly is playing team owner Jerry Buss and Segel, assistant coach Paul Westhead. In the scene, the team -- wearing "LOS ANGELES LAKERS WORLD CHAMPIONS 1980" t-shirts -- celebrate with the Walter A. Brown trophy (now the Larry O'Brien trophy, since 1984).

Also in the scene is actor Solomon Hughes ... who's playing Kareem. Actor Quincy Isaiah, who's from Magic's home state of Michigan, is portraying the legendary point guard.

The Showtime Lakers -- led by Johnson and Abdul-Jabbar -- were basically unstoppable ... winning 5 championships in the 1980s. ('80, '82, '85, '87, '88).

And, their impact wasn't just felt on the court ... when Buss bought the team in 1979, he made Lakers games the place to be -- and be seen.

He introduced the Lakers Girls and live music at The Forum ... and the crowds often featured A-list celebs sitting courtside.

The series -- inspired by Jeff Pearlman's book, Showtime: Magic, Kareem, Riley and the Los Angeles Lakers Dynasty of the 1980s -- will also feature Adrien Brody (Pat Riley), Michael Chiklis (Red Auerbach) and Sally Field (Jessie Buss).