Where new levels of quality go, new levels of parody are sure to follow. So it makes sense that a strong run of historical sports documentaries, particularly from ESPN's 30 For 30series, would give rise to a spot-on mock-documentary like HBO's 7 Days In Hell, airing Saturday night.

7 Days In Helltells the (made-up) story of an epic, week-long tennis match in 2004 between two superstars: Aaron Williams, an American self-styled rock star sporting an extravagant blond mullet, and Charles Poole, a nervous British prodigy terrified of disappointing his mother. Williams is played by Andy Samberg, which is not so surprising, but Poole is played by Kit Harington, best known as Game Of Thrones' Jon Snow, which is, at first glance, a little bit more likely to provoke a response not so much hostile as curious. Something like ... "Really."

Williams is stylistically Andre Agassi in a lot of ways, but he's been mushed up with the mythology of, of all things, the Williams sisters. Aaron is, the film explains, the adopted brother of Serena and Venus, a situation Serena (one of many, many familiar faces to pop up playing either themselves or others) describes in an interview as a "reverse Blind Side." He becomes a hard-partying aggressive doofus, very much in the Samberg tradition of same. Charles, on the other hand, struggles under the thumb of a controlling mother (played by Mary Steenburgen) and just wants to play tennis.

The least effective parts of the film are the ones that actually focus on how this tennis match stretched out for seven days. While some of the excuses for its dragging on are amusing, they eventually get a little desperate and ... um, grasping. Well, you'll see. Much more delightful are all the little comedy baubles twinkling from various corners: an outrageous, totally straight-faced turn from David Copperfield; John McEnroe coming right up to the edge of having too much fun with his own persona but then basically getting it right; Michael Sheen as a sweaty, lecherous talk-show host; and especially a completelyunnecessary sidebar into the history of Swedish courtroom artists.

It was a smart move to cast somebody like Harington opposite Samberg, because it keeps the entire thing from feeling like a long Saturday Night Livesketch, and while Harington is very funny, he's not funny in the cranked-up way Samberg (and Armisen and Will Forte) can be. He has the carriage of a traditional comic actor instead of a sketch comic.

This is the kind of comedy special — at an efficient 42 minutes — that stays afloat using the strategy people use if they're racing across a series of floating buoys: you move fast, you don't stop long enough to sink, and you don't try to do it for too long. Near the end, 7 Daysstarts to drag just a little, but they don't try to make the bit more than it is — they don't try to make it a feature film or build it into a series. It's a goofy, exuberantly dirty little one-off, where Samberg and Lena Dunham and Fred Armisen and a lot of other people wear very silly wigs and there is an imposing amount of nudity (mostly male, mostly frontal, and, health concerns cause me to hope, some percentage prosthetic).

There's so much going on in web comedy that's breaking up the expectation that everything will be (1) a sitcom, (2) a stand-up special or (3) a sketch show that it's good to see things like this that suggest that television can absorb some of that formal experimentation and run something like this that, a few years ago, would have seemed like a much more unlikely project than it does today.

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