In the immortal words of Kermit the Frog, it's not easy being green. But Kermit doesn't know what hard is: it is much, much more difficult to be a Teletubby. This is a fact that you are not likely to hear from the mouth of a Tubby; in fact, the actors--yes, those are real actors inside those bright, baby-shaped alien outfits--are contractually forbidden to talk to their adoring public. "My favorite color is green," says Dipsy, played by John Simmit, rolling his eyes. "That's all I'm allowed to say." And if the Teletubby creators had their way, we might not even know that much. Why the secrecy? "We don't want to destroy the magic," people involved with the show explain again and again, obviously infected by that numbing, Teletubby-like repetition that mesmerizes children. Or, as the show's co-creator Anne Wood says, "We want to preserve the whole reality of the Teletubbies."

Reality is not exactly the first word that springs to mind when thinking of Tinky Winky, Dipsy, Laa-Laa and Po. The first television show explicitly designed for the one- to two-year-old set, it centers on the comical activities of four fuzzy creatures who speak in baby talk, eat Tubby Custard ("Tubby Tustard!"), share "big hugs," and have TV antennas on their heads and TV screens on their stomachs that transmit short film clips showing real children. In other words, this is a TV show about infants, for infants, that extols the wonders of, among other things, television. So what? say kids'-TV veteran Wood, 60, and co-creator Andrew Davenport, 33, a trained speech therapist and former performance artist; they insist that Teletubbies helps children acquire language skills. "Children are able to make their own meaning from it," says Wood. "We don't have an adult on there telling them what to think."

Of course, since the target audience does not yet speak, we don't know what they do think--but kids plainly love Teletubbies. About 2 million people in Britain have watched it daily since its launch last year; it has been sold to 22 countries; and since premiering on PBS in April, it has swiftly landed alongside Barney and Sesame Street in the top five of the system's kids' shows.

Occasional British-style tabloid feeding frenzies and endless controversy over its educational merit have left the folks in Teletubbyland--actually six acres of farmland outside Stratford-upon-Avon--more than a little press shy. But TIME was recently permitted a rare look at the filming of two sure-to-be-classic episodes: "Don't Pull That Lever, Dipsy" and "Laa-Laa Has an Orange Ball." As Tubby body parts roll by in wheelbarrows and crew members carefully place live rabbits and racks of fake flowers on the Day-Glo green Home Hill, Davenport cautions, "There's a lot of intervention that happens before it reaches the screen. It's speeded up; it's colored sometimes; the characters are cut to make it look as though they keep their heads on for more than 10 minutes."

Ten minutes? The Teletubbies should be so lucky. A casual stroll through the grounds will usually turn up at least one sweaty Tubby slumped over his tea or reclining in a Tubby bed inside the Tubbytronic Superdome, their spaceship-like home. Though onscreen the Fab Four appear to be a baby-friendly size, in "person" they are gargantuan, bigger than Barney, bigger even than Big Bird. Po, the smallest, is 6 ft. 6 in., while Tinky Winky looms around 10 ft. tall. This makes for a costume that weighs more than 30 lbs. And if the performers, who see and breathe through the mouth holes, keep their heads on too long, there is a danger of carbon-dioxide buildup. Surely a better head could be designed? "The artists can cope with it the way it is," says production manager Nick Kirkpatrick.

Just barely. During the climactic scene in "Laa-Laa Has an Orange Ball," Laa-Laa (played by Nikky Smedley) doodles along singing her little song, "La la la la la." Upon spying an enormous orange ball, she halts in astonishment, picks it up, bounces it a few times, then throws it into the air Mary Tyler Moore-style. The sequence takes maybe 30 sec., but the moment Laa-Laa finishes, someone cries "Heads off!" and a stool is thrust under her while her dresser races over to whip the yellow head off, revealing the petite Smedley sweating and gasping as though she has run a marathon. "Doing the voices, that's good fun," Smedley says, as an unamused publicist hovers. "The costume bit is quite hard." She gulps some water. "We have physiotherapy every week, thank God." So is this a good job? Says a staff member: "If you spent your life anonymous, inside a suit, sweating your guts out, how do you think it feels?"

To match the scale of the Teletubbies, everything else on the set is also bizarrely off-size, including the rabbits seen in many scenes, which are bred especially for the show. The size of small sheep, the rabbits are pretty docile--except when they start "bonking" on-camera, their breeder admits. "Oh, don't write that!" she wails. "I'll lose my job." As Kenn Viselman, president of the Itsy Bitsy Entertainment Co., which is marketing the show in the U.S., puts it, "Everything about it is choreographed: the number of flowers on that hill, the ply on their fur. They fired an actor because he decided to fall off the chair more than they wanted him to."

The precise choreography is, however, essential. Long before anyone knew the show would be a hit, Wood and her company, Ragdoll Productions, put up more than three-quarters of a million dollars to build Home Hill, with the BBC kicking in millions more. And Ragdoll has promised the BBC a staggering 260 episodes--nearly 100 a year.

All this intensive, 11-hour-a-day labor has a tremendous potential payoff, not only for Wood and Ragdoll but also for PBS, which has a piece of the spin-off action that Viselman estimates could be worth some $2 billion in retail sales. What does Viselman, who merchandised Thomas the Tank Engine, have planned? In addition to assorted dolls, expect to see Tubby slippers, backpacks, puzzles, videos, pajamas, books, board games, baby bottles, cups, key chains, stacking toys and, as the Tubbies would say, "Again, again!"

Wood claims that such merchandising is simply "now a part of life for children" and that parents "expect it." But the Tele-stuff, more than the critters themselves, has some children's advocates worried. "It's a very sweet little show," says Kathryn Montgomery, president of the Center for Media Education. "But do we want to create a media culture which is aggressively marketing to younger and younger children?" The answer, emanating from that strange place over the hills and far away, sounds a lot like yes.