THERE ARE two kinds of people, those who've never heard of the Wiggles and those who know all the words to "Fruit Salad." There's a word for those in the latter group: parents. The Australian children's group, long enormously successful at home, is increasingly ubiquitous in the United States. Even if you've never seen the band's top-rated show on the Disney Channel, chances are you've run across its DVDs, CDs, books or toys. The four guys in the primary-color turtlenecks? That's them.

The Wiggles are a classic four-piece pop combo -- except for the fact that their infectious, upbeat songs are about things like teddy bears, ponies and looking both ways before you cross the street. Now in its 13th year, the band is the most successful children's act in Australian history -- the Wiggles are the country's fifth-highest-paid entertainers (Nicole Kidman tops the list). Their live performances are a hot commodity: Last fall they played 12 sold-out shows at Madison Square Garden, besting a record held by Bruce Springsteen. The group performs four concerts at the Patriot Center this weekend.

For those who think of the Wiggles -- Greg Page, Murray Cook, Anthony Field and Jeff Fatt -- as four grown men who are known to share the mike with a polka-dot dinosaur, the band's rock 'n' roll credibility can come as a surprise. Both Field and Fatt played in the Cockroaches, a moderately successful '80s band that scored Top 10 hits in Australia and toured with quirky Aussie rockers Mental as Anything. Field, speaking by telephone from Sydney with his infant daughter, Lucia, cooing in the background, recalls those days. "We played all around the coast of Australia, the surf clubs and things like that," he says. "We had a great time."

After the group disbanded, Field enrolled in Sydney's Macquarie University to study early childhood education. It was there that he embarked on a portentous class project with fellow students Page and Cook. Later, as the class project -- writing and performing songs for children -- morphed into a professional concern, Field recruited former bandmate Fatt to join the group. (All four members play instruments and have a hand in writing the group's material.) Their first CD, "The Wiggles," came out in 1991. "We were going 'round Australia selling cassettes and CDs out of a suitcase backstage, which is how we started at first, then we started selling videos," Field says.

As for performing, Field says it isn't substantively different than the job he trained for at university. "All of us, well, three of us, are early childhood teachers, preschool teachers, and as soon as you become a preschool teacher, any self-consciousness you had just goes out the door because you're educating, but basically you're also entertaining a class of 30 3-year-olds." Does he feel silly when called upon to, say, walk like an emu? "It's funny -- you don't," he says. "You never get self-conscious making funny faces. It's like doing different voices for your own child. You've got to be a little larger than life and a little happier than you would be talking to one of your peers. It would be a bit strange if you were bouncing around saying, 'Hey!' "

The group's transition from moonlighting preschool teachers to touring band to multimedia entity was not instantaneous. Fields says the group spent five or six years on the road before it broke through to a wider audience. (The band tours heavily to this day, averaging 500 concerts a year.) "It was really strange because we were playing little places, and then we did a show in Australia called 'The Midday Show.' I don't know if there's something in the daytime there that everyone watches -- it's like 'Oprah,' I suppose. After that, people started recognizing us as the Wiggles in the street, and it sort of changed things.

"The good thing about doing what we do also is that when people recognize you they're very nice because their children are happy and you've contributed to it a little -- for 10 minutes or half an hour."

The Wiggles TV world is color-coded: Field wears a blue shirt, Fatt a purple one, Page yellow and Cook red. In addition to being readily identifiable by color, each Wiggle is distinguished by a few simple behaviors: Greg does magic, Murray plays the guitar, Anthony eats too much and Jeff perpetually falls asleep (hence the show's catchphrase, "Wake up, Jeff!"). Field says their characterizations aren't that far off. Murray, for instance, is a die-hard music fan. "We all love music, but I think he's got the biggest CD collection," Field says. "The food thing is me -- I've always got a new diet. Jeff is laid-back and so relaxed and such a nice, peaceful man."

As it happens, Jeff's sleepiness is no accident. "Jeff is not early childhood trained," Field says. "When we first started to do shows, he came out of the Cockroaches with me, and he had no idea what to say to a preschool audience. We put our heads together and thought, 'If you really want to be popular with the children, you've got to give them power over you.' And he is the most popular because they get to wake him up." Field is quick to point out that Fatt is a good actor. "In real life, Jeff doesn't like to be woken up when he's asleep," he says confidentially.

Field says his university training has been indispensable. "We go back to it all the time," he says. "We know, hopefully, where children are coming from. For example, a 2-year-old is totally egocentric -- the world revolves around them -- and so it's almost like you've got to come from that perspective when you're onstage. How you include them is 'Can you help us wake Jeff up? We need your help -- we can't do this without you!' " In the same vein, the Wiggles never tell kids what to do. "Children love challenges," Field says. "So 'Can you point your fingers and do the Twist?' is a lot better than 'Point your fingers and do the Twist!' Just add the two words and the kids will go, 'Yeah, I can do this -- look!' "

Like their lyrics and their look, the Wiggles' live show is uncomplicated. "The sets are really simple, what we say is really simple. If we put too much in, we might scare the kids," Field says. "We have the lights up in the audience a little higher than you would at an adult show, so they aren't scared of the dark or anything like that. We think if we put in too many pyrotechnics you're going to startle some kids, and it'll be their first experience of a show. It's a concert, but mainly we hope children move their bodies, have a laugh and join in the fun." The big special effect being unveiled on the band's current tour is: trampolines. "It'll be lots of laughs," Field promises.

You've heard of the fifth Beatle? There's also a fifth Wiggle -- and a sixth, seventh and eighth. The Wiggles tour with their human sidekick, Captain Feathersword the Friendly Pirate, and their three non-human ones, Wags the Dog, Henry the Octopus and Dorothy the Dinosaur. "Children respond to animated characters sometimes more than they do to real human beings -- adults and things," Field says. "We can sort of talk to the children through Dorothy and let Dorothy talk to the children. It's great having them come on, and there's a different feeling when they come out onstage. When Dorothy first comes out, it's like Elvis coming in with a support band -- raaaaaaahhhhhhhhh!"

Although his own musical taste runs to Julio Iglesias -- "there's not a day goes by I don't listen to Julio's tango album," he says -- and tango legend Carlos Gardel, Field knows a thing or two about his audience. "We could have put a lot more words than "hot potato" in "Hot Potato," he says, laughing. "We would have put a guitar solo in there or something. We get straight to the point in our songs -- there's no time for mucking around."

Field's own favorite Wiggles tune is "Rock-A-Bye Your Bear," a gentle lullaby that has accompanying hand motions. "My wife sings that to our 6-month-old baby now," he says. "It's a really good one for little kids under 2 because, if there's another child, they can do the actions next to each other -- kids that age don't exactly like to hold hands and dance. It's still their song, but someone else can do it, too."

Parents may be gratified to hear that Field sometimes finds the Wiggles' material as maddeningly catchy as they do. "When we first wrote 'Fruit Salad,' I couldn't go past fruit salad without that song going in my head," Field says. "Sometimes it still does, 12 years later." That may be part of the reason it's arguably the band's most popular song and a showstopper in concert. "I think it's a fun song," he says. "It's like a bubblegum song from the '60s.

"It's a great world we enter into on that stage. I think it's a good place -- where people can get excited about a song about fruit salad. With all the trouble in the world, why not?"

THE WIGGLES -- Appearing Saturday and Sunday at the Patriot Center. * To hear a free Sound Bite from the Wiggles, call Post-Haste at 301-313-2200 and press 8117. (Prince William residents, call 703-690-4110.)

With success among the preschool set, the Wiggles have gone from Down Under to top of the world.