The Ninja Turtles’ Kind and Costly Mutation : Kidvid: The heroes’ ‘friendlier, warmer’ $20-million sequel opens at movie theaters Friday. The quartet will also increase their appearances on the tube, in the stores and at the breakfast table.

The first time out, no one knew what to expect from a movie starring guys in turtle suits. When “Teenage Mutant Ninja Turtles II: The Secret of the Ooze” opens on an estimated 2,500 screens Friday--less than a year after the original--expectations are so high that executives at the producing Golden Harvest Films and New Line Cinema are already talking “Part III,” expected to open late next year.

Those same executives claim that the sequel will be even “more accessible” than “Teenage Mutant Ninja Turtles,” which rang up $135.5 million in box-office receipts last year in the United States and Canada.

Budgeted at $20 million--twice the cost of the original--the sequel will reportedly be brighter and more colorful than the original, which was dominated by a gray, gritty look. “It will be more fantasy-like--friendlier and warmer,” says David Chan, who co-produced both films.

In response to some parents’ complaints, it will also be less violent than the first, which had a good deal of bonking and kicking and use of weaponry--though there was no bloodshed. But, insists Chan, this doesn’t mean the Turtles have given up their trademark fighting skills. Only that they will be brandishing humor more often than weapons.

Says Chan: “We’re not changing the nature of the Turtles. They are what they are. But there are all kinds of ways to fight.”

Indeed, when a fight breaks out in a deli, the Turtles wield . . . sausages.

When the first Turtles movie was released, there was a concerted marketing effort to keep the Turtles a surprise. The poster revealed only a glimpse of the title characters’ faces peering from a manhole, along with the declaration, “Hey, dudes, this is no cartoon.”

Although “Turtles II” promises secrets in the title, there’s no secret about its stars. The teen-age terrapins are emblazoned across marketing materials everywhere. Their costumes, designed by Jim Henson’s Creature Shop, are the subject of a segment in the sequel’s electronic press kit, which is being sent to TV outlets.

Meanwhile, marketing executives at New Line are readying to roll out the green carpet--and the hype. There will be music videos, including one from rapper Vanilla Ice (who puts in an appearance in the movie) doing “Ninja Rap,” with the Turtles providing back-up dance. Plus promotions at J.C. Penney, the film’s “official retailer.” There will even be a promotional tie-in on a Turtles cereal.

The sequel will be launched with glitzy benefit premieres in 30 top markets. Locally, a sell-out crowd gathered at the Universal Cineplex Odeon Theater.

The faceless actors inside the Turtle outfits will also be participating in celebrity interviews, including one with Barbara Walters, who apparently will grill them in character for her post-Oscar show Monday on ABC.

When it was released last year on March 30, “Teenage Mutant Ninja Turtles” shocked just about everyone with opening weekend ticket sales of $25 million. It went on to become the top-grossing independent film in history and ended up fourth on the year’s list of commercial hits.

Based on a comic book, which in turn launched a popular toy and a syndicated animated series, the Turtles movie has become impossible to ignore. The characters’ likenesses are emblazoned on an estimated 300 products from some 100 domestic licensees. Worldwide, there are another 800 Turtles’ licensees, and more are anticipated as the Turtles’ TV show travels around the globe.

Retail sales of Turtles items came to an estimated $1 billion last year, about $100 million more than the Simpsons. Mark Freedman, president of Surge Licensing, the licensing agent for the Turtles, says his aim is to make the Turtles “classics”--as much a part of Americana as Mickey Mouse, Donald Duck, Bugs Bunny or the Muppets.

For a sampling of Turtlemania, consider:

* The first Turtles movie sold an estimated 9 million to 10 million cassettes in the United States and Canada. And the movie itself has proved a hit in such countries as Great Britain, Australia, Spain and Finland, though the Turtles are not that well known in Scandinavia.

* Their hourlong animated series, which airs Saturdays at 8 a.m. on CBS, has made the Turtles the No. 1 stars of kidvid. They also star in a half-hour animated series, syndicated by Group W Prods., which airs five days a week in 153 markets covering 93% of U.S. households. (Locally, kids tune in daily at 7 a.m. on KCOP Channel 13.)

* The Turtles’ live touring stage show, launched in September, is expected to continue through the summer. Come fall, a new edition will hit the road.

* Archie Comics, which ships 500,000 copies of the Turtles’ monthly comic book, recently began shipping a Turtles’ spin-off comic called Mighty Mutanimals.

* Like Snoopy and Garfield, the Turtles now have their own syndicated comic strip, through the Los Angeles-based Creators Syndicate, which also handles strips like “B.C.” and “Mama.” The strip debuted in some 300 papers, including The Times, in December--making it 1990’s best-selling new strip.

* The sale of Turtles’ toys by Playmates Toys--the largest licensee of Turtles’ items--is expected to top $400 million for 1990, up from $115 million the previous year. Playmates recently introduced 90 new Turtles’ toys--bringing its Turtles’ line to 165 products.

* There are shelves of Turtles food products, including Ralston Purina’s Turtles’ cereal--in the shape of ninja nets (which the Turtles use to trap bad guys), with multicolored marshmallow turtles and weapons. Hostess, a division of Ralston Purina, recently released a green-glazed vanilla-filled pie that promises “puddin’-power,” a reference to the ooze which mutated the Turtles. Also new from Ralston Purina: the snack food, Pizza Crunchabungas.

The Turtles’ phenomenon was hatched in 1983 when Peter Laird and Kevin Eastman began self-publishing a black-and-white comic that spoofed superheroes with its story of four unlikely crime-fighters who do not possess super powers, and happen to be turtles.

As the Turtles’ saga goes, they were originally average, ordinary pet store-size turtles. But as babies, they were dumped into a New York sewer where they happened upon a toxic ooze, which turned them human-size. A rat named Splinter--once the pet of a ninja warrior--also mutated and became their spiritual leader. They all live together in the sewer.

“Each turtle is unique,” says Turtles co-producer David Chan. “Just like brothers everywhere, they fight among themselves. But they also unite.”

Actor Michelan Sisti, a Broadway veteran of 20 years, who returns to “II” to again play Michaelangelo, says: “Kids identify because the Turtles are brothers who aren’t shy about caring for one another.”

Michael Pressman, who directed the Turtles’ sequel, believes kids relate, “because the Turtles are outcasts--mutants who are also witty, and who cut loose. The Turtles are like the Marx Brothers for kids.”