It’s risky business, turning a TV show into a film. Oftentimes, humor that works well in half hour blocks falls flat when stretched out to 90 minutes or more. Sure there have been successes: “South Park,” “Borat” and the various “Monty Python” vehicles. But there have also been some abysmal failures, like Comedy Central’s recent attempt at adapting the short-lived “Strangers with Candy.”

“Reno 911!: Miami,” an adaptation of another Comedy Central show, is, unfortunately, one of the latter.

For anybody unfamiliar with the program, “Reno 911!” is what you get when a bunch of improv actors attempt to lampoon “Cops.” Every week, the bumbling crew of Reno sheriffs gets into a series of awkward situations involving failed drug busts, failed prostitution stings, failed traffic stops, failed … well you get the idea. The show doesn’t rank with Comedy Central’s best offerings (“Daily Show,” “Colbert Report,” “South Park”) but it has its moments.

In the movie, the Reno sheriffs all head to Miami to attend a national police convention (what happens to Reno with no law enforcement is never expounded upon). When closet-homosexual-with-a-fetish-for-hot-pants Lt. Jim Dangle (Patrick Lennon) and his crew get to the resort, they find that their reservations have been lost and have to go across town to stay in a seedy motel.

But during the first night of the convention, an act of bioterrorism forces the Centers for Disease Control to quarantine all 2,000 police officers in their hotel, leaving only our beloved Reno cops to patrol the streets of Miami and try to get to the bottom of the outbreak.

But the plot can really be described much more succinctly: If you thought those wacky Reno sheriffs were dumb when they were working their home turf, just wait till you see them in Miami!

Unfortunately, hilarity never really ensues.

The film does have its moments. One early scene features the Reno sheriffs running around outside their motel rooms, intoxicated, providing an opportunity for the thinly veiled intradepartmental sexual tension to run loose. You see, each of the eight sheriffs has a crush on one of the other sheriffs, but the feeling never goes both ways; it’s a sort of love octagon. Soon enough, the sheriffs are forced to, er Ö take matters into their own hands.

It’s one of the funniest scenes in the film, but it also exhibits the movie’s primary flaw: It doesn’t trust itself and repeats the same joke too many times, losing a little of its luster with each reprise.

As with the show, the funniest moments are the little awkward throwaway jokes and one-liners. But with an hour and a half – and a lot bigger budget – to kill, the cast members (who also wrote the film) can’t seem to tell when enough is enough; almost every time they reach for a really big laugh, the gag falls flat on its face.

“Reno 911!: Miami” is saved in part by a series of short, but funny, cameos. Patton Oswald steals every scene he’s in as Deputy Mayor Jeff Spoder, and the three guys from Comedy Central’s “Stella” (Michael Ian Black, Michael Showalter and David Wain) are their usual funny selves in their all-too-brief appearances. Unfortunately, Paul Rudd, in a more extended role as a Tony Montana wannabe, doesn’t fare nearly as well.

Though the film provides enough exposition that one needn’t necessarily be familiar with the show to catch up, it is clearly geared toward the cult fans of the series. That said, any “Reno 911!” fan would probably be better served to find his or her three favorite episodes and play them back to back to back. It’s there, in the scaled-down confines of a low-budget, half-hour show, that the cast is able to play to their strengths.