The situation's well in hand in "Fraggle Rock," which is not only a mythical place but also an extremely actual television program--the first original weekly series to be offered by the pay-TV service Home Box Office, and the latest fetchingly whimsical enterprise from Jim Henson's Muppets. The series premieres on HBO at 7:30 this evening; episodes bow on Mondays, then are repeated three times within the week.

Fraggles are small, semi-furry beings who live in a cave that is reached through a hole in the wall of the home of an eccentric inventor named Doc. The inventor, a member of the National Society of Tinkerers, is played by a real human being, Gerry Parkes; every other major character is played by one of a vast army of newly designed Muppets, including Doc's dog, Sprocket.

Among the major Fraggles are the good-natured Gobo, the naive Mokey and the gullible Wembley. The Fraggles regularly receive illustrated dispatches from their nomadic uncle, Traveling Matt, whose name, of course, is one of the Muppeteers' little puns. A traveling matte is a cinematic device for making things appear to be where they are not. The Fraggles, like all good Muppets, are triumphs of such illusory tactics.

It's always hard to predict what children will enjoy and respond to. Chances are they will find the demanding and temperamental Sprocket more recognizably amusing than the Fraggles themselves, since their identities tend to be not quite so distinctive as the old Muppet crowd. Kermit, Miss Piggy and their friends are apparently consigned now to the slightly ignoble immortality of Rerun Heaven.

Clumsily enough, HBO did not supply tonight's premiere episode for a preview. Instead it supplied next week's and a future episode yet to be scheduled, but the sampling indicates a fresh and funny approach to mild, painless moralism; a saucy cuteness that's never merely precious or condescending; and adventures that exclude neither tots nor grandparents nor anyone in between from the target audience.

Written by Muppet veteran Jerry Juhl and directed by executive producer Henson, "Fraggle Rock" features, in addition to the Fraggles, the menacing and enormous Gorgs--a king who talks like a southern sheriff, a queen reminiscent of Margaret Dumont and their imbecilic son. They have no subjects over which to rule and so spend their time tracking, thwacking and attempting to throttle Fraggles.

The Fraggles, meanwhile, are not innocuous, like Smurfs; in fact, they have their termitic side. They eat the little buildings that are perpetually erected by Doozers, who are even smaller than Fraggles and who don't mind their buildings being eaten at all. In a future show, when the well-meaning Mokey gets the Fraggles to stop eating Doozerisms, the Doozers are mortified and prepare to leave. The moral of this episode is don't mess with the balance of nature.

Unfortunately, the tale could also be seen as rationalizing the subjugation of one people by another--but that would be so picky.

It hardly flies in the face of precedent that the first weekly series on HBO would be produced in another country, and not a mythical one, either (Canada), and be the product of a proven commercial powerhouse, not the brainstorm of some newly discovered innovator. HBO always plays it safe; it is only a partner in "Fraggle Rock," one cog in a byzantine financing scheme, and the programs come complete with spaces for commercials if the series plays in other countries or, in the future, on free TV in this one.

But none of that detracts from the fact that "Fraggle Rock" looks to be a lovely place to visit after dinner.