Ghost of Serpico

David Shaber's original script for Nighthawks was developed as the basis for a second sequel to French Connection (with Richard Pryor as a wisecracking cop who teams up with Popeye), but Gene Hackman refused to reprise his role as Popeye Doyle again and the script was re-worked for Sylvester Stallone and co-star Billy Dee Williams. From the long locks and facial hair of a beefier than usual (at the time) Stallone, it's clear that the filmmakers (or the star himself) also had another famous '70s real-life and cinematic New York cop in their heads: Frank Serpico.  They're not so interested in the politics or methods of Serpico, nor the realism or tragic qualities of that film, but Stallone's sunglasses, beard, and long hair are surely meant to inspire memories of Al Pacino in his iconic role on a purely surface level.

Stallone's beard was apparently suggested by then-girlfriend Susan Anton, seen here with Warhol, receiving one of Sly's characteristic fake punches to the chin.

In one scene early on, Deke DaSilva (Stallone) and his partner Fox (Billy Dee Williams) scale a tenement via fire escape in order to make a bust.  It's reminiscent of a moment in Serpico in which Pacino uses the same method to enter a building.  I've mashed up these two scenes, as the parallels in costuming and physical appearance are rather striking.

The same scene in Serpico also has a shot of Pacino walking down a street and into building, which is similar to a shot in the actor's later vehicle, Cruising, in which he lazily swaggers home to his girlfriend (Karen Allen) after another night out in the Meatpacking District.  His appearance is completely different in terms of clothing and hairstyle from that of Serpico, but the mise-en-scene and the actor's movements are nearly identical.  In terms of performance, the two scenes reveal an aspect of an actor's bag of tricks--in this case, the way he moves to suit a character and the camera--that is not cited as often as his verbal abilities.