A mural on the outside wall of a small video store on East Carson Street in the South Side features four turtles, wearing bandanas and grimacing as if going into battle on a bright green background.

	Bill Wade, Post-Gazette Milton Barr, 20, shows a homemade mutant turtle mask used at his South Side movie and game rental store. Click photo for larger image.

There are other images, too, including a wolf wearing what appears to be a red robe and a villainous-looking, armor-clad character.

The mural -- along with a flier sent out by the business, MIB Ninja Entertainment -- has become the subject of a trademark infringement lawsuit in federal court.

Mirage Studios Inc., the company that owns the trademark for the Teenage Mutant Ninja Turtles, claims the store is illegally using the popular comic book-turned-movie characters for advertising purposes without permission.

The lawsuit, filed late Monday, seeks an injunction to keep the video store from using the images, an order requiring that all materials featuring the characters be destroyed and monetary damages.

But Milton Barr, 20, who has operated the store on the South Side, and another on West Liberty Avenue, for about six months, called Mirage Studios' demands "ridiculous," and a classic example of a big company going after the little guy.

"Under the First Amendment, I have the right to paint whatever I want, as long as I don't make money off of it," Mr. Barr said.

But Michael Madison, a professor of trademark law at the University of Pittsburgh, said that's not true.

"There is an idea of a free speech defense, but it's very narrow, and it almost never applies when you're using a trademark to advance your business," he said. "They are using the Turtles in connection with a for-profit business."

Mr. Barr, who says he enjoys the Teenage Mutant Ninja Turtles, called the mural an adult version of the theme.

He also said that he believed trademark law allowed him to use some version of the characters if they were 15 percent different from the originals.

Looking at the mural, he noted differences from the Mirage characters in his turtles' shapes, smiles, color, chests and masks.

But Mr. Madison said there is no magic number for difference. Instead, what really matters is the "likelihood of confusion," for the public: Would members of the public likely be confused by the video store's use of the Turtles and think that it is in some way connected with the characters?

The more details taken out of the design, he said, the better defense a person would have against a trademark claim. But crime-fighting, anthropomorphized turtles who walk upright are pretty specific, he continued.

Mirage contends that the MIB Ninja Entertainment stores also have used its Shredder character -- the Turtles' arch enemy -- in advertisements.

Mr. Barr acknowledged that occurred under a former investor at the business, but not since he's been in charge.

In addition to the trademark infringement allegation, Mirage also filed a claim for dilution, saying that the video stores are diluting the distinctive quality of what they call famous trademarks.

That claim does not include the "likelihood of confusion," standard, so even if Mirage would lose the trademark infringement case, Mr. Madison said, it could still win on dilution.

The Teenage Mutant Ninja Turtles first appeared in comic books in 1984. They became the subject of an animated series three years later, and most recently were released in the form of a computer-animated movie in March.

"With the movie, I get the sense the marketing machine is gearing up again," Mr. Madison said.

That means the company has to protect its trademark by policing any unlicensed use of it. Sometimes that means sending letters to cease and desist -- Mr. Barr received two -- and sometimes it might mean filing a federal lawsuit, he said.

"Ultimately, big companies have the power and the money most of the time to get what they want. A little video store on the South Side -- I'm guessing is not likely to have the resources to fight this."