The Lonely Island, the comic hip-hop trio consisting of Andy Samberg, Jorma Taccone and Akiva Schaffer, exists in a place somewhere between satire of terrible mainstream rap and affectionate tribute.

In short form, in the songs like “I’m on a Boat” that powered their beloved “Saturday Night Live” digital efforts, the absurd-yet-credible style effectively lampoons the genre’s occasional predilection for narcissistic nonsense.

At feature length, as proven by the trio’s first movie “Popstar: Never Stop Never Stopping,” the satirical edge progressively dulls and you leave the theater with the sense that these guys might enjoy the terrible music and culture they’re ridiculing just a bit too much for comfort.

That makes this mockumentary, in which Samberg plays boy-band-member-turned-successful-solo-rapper Conner4Real, something of an inconsistent experience. Eventually, the trio (all three co-wrote the script, while Taccone and Schaffer direct) run out of new and interesting ways to mock the industry and these characters. The subsequent shift toward sentimentality, all but inevitable in any mainstream movie, effectively forces the audience to take Conner more seriously than he deserves, and nuance isn’t really The Lonely Island’s strong suit.

Hilarious song parodies are their specialty, of course, and the movie is at its finest when it offers a succession of wonderful tunes in its early moments. Conner abandoned The Style Boyz and fellow members Lawrence (Schaffer) and Owen (Taccone), for superstardom. This means trading kitschy hits like “Donkey Roll” for songs such as “Equal Rights,” in which Conner’s earnest plea for same sex rights is interrupted by frequent reminders that he’s not gay.

As expected, the picture offers a mass of A-listers playing characters in cameos or making talking head appearances as themselves (everyone from Maya Rudolph to Ringo Starr to Questlove and honorary Lonely Islander Justin Timberlake). The men of The Lonely Island have proven themselves to be masterful tweakers of celebrity imagery, and the movie gets plenty of comic mileage from the phalanx of big names taking part in the circus.

It’s simply hard to take any of this seriously, and even harder when it becomes apparent that they expect you to do so.