Could the Phillie Phanatic really become a free agent?

The fans are flustered. The team is fighting back in federal court. The mascot’s creators say they never wanted it to come to this.

And yet, the question of the Phillie Phanatic’s free agency looms larger than a 6-foot-6, 300-pound flightless Galapagan bird brandishing a ballpark hot dog launcher. Will Philadelphia’s beloved green mascot be forced to pack his bags over a copyright controversy?

While the case is complicated by the Phanatic’s unusual creation story, and distinctions between copyright and trademark, things aren’t likely to end in a farewell to the mascot, legal experts say.

In a federal lawsuit filed this month, the Phillies accuse Bonnie Erickson and Wayde Harrison — a puppet- and costume-creating couple responsible for designing the Phanatic — of threatening to withdraw from a 1984 agreement to let the Phillies use the mascot “forever.”

If the Phillies do not renegotiate with Erickson and Harrison for “millions of dollars,” the lawsuit asserts, the pair has threatened to “make the Phanatic a free agent” and sell the rights to the furry, cheesesteak-guzzling biped to another team.

In a statement, Harrison and Erickson called the litigation “incredibly disappointing,” adding that they “very much want the Phanatic to remain the Phillies mascot.”

“At the Phillies’ request more than 40 years ago, we created the Phanatic, giving him a story and a life.... His value has grown with his popularity, and we felt that the Phillies franchise never offered a reasonable payment to extend the Phanatic’s license,” the statement reads.

The case marks an unusual intersection of copyright and trademark law.

A trademark protects “a word or logo or thing that is used to identify a brand,” said Amy Landers, a professor and director of the intellectual property law program at Drexel University’s Kline School of Law. “When we see the Phillie Phanatic, we think of the Phillies. When we see the Coca-Cola logo, we think of the soda. It’s a way to protect what people advertise.”

Copyright, she said, “is a formal way of protection for creative expression, like books, art, and movies, and more recently, for costumes and clothing.”

The Phillies have trademark rights to the Phanatic, and the dispute is over a copyright agreement.

An athletic team typically contracts designers to build a mascot and pays a flat fee for their services and rights to the creation, said Paul Kennedy, an intellectual property attorney at Pepper Hamilton.

“But that’s not how this evolved,” he said. "Harrison and Erickson retained some of their rights to the copyright, and now want more money for the success of the Phanatic.”

In 1978, when the Phanatic first sprung onto the Veterans Stadium field and into Philadelphians’ hearts, the Phillies paid Harrison and Erickson $3,900 for the creation of the mascot costume, but left the Phanatic’s copyright rights to the duo. It was a move then-Phillies vice president Bill Giles made to save $1,300, and later regretted. In fact, in his 2009 autobiography, Giles called it “the worst decision of my career.”

“Once they saw how successful it was and how popular it was, then they chose to buy the copyright from us,” Erickson, who worked with Jim Henson and created famed Muppets Miss Piggy, Statler, Waldorf, and more, told WBUR in Boston last month. “It cost them more.”

It cost $248,700 more. In 1984, the Phillies bought the copyright rights for $250,000 from Harrison and Erickson in an agreement the team’s lawsuit said was “forever.”

But artists can renegotiate copyright after 35 years, to capitalize on the success of their creations, Landers said. That’s what Harrison and Erickson are trying to do.

In their lawsuit, the Phillies argue they are a co-author of the Phanatic character, helping Harrison and Erickson to bring the mean, green, slightly obscene mascot to life — a move that bodes well for the team’s argument, Landers said.

That way, a judge may be forced to look at Harrison and Erickson’s copyright on the shag rug costume separately from the Phanatic’s mischievous antics on the field, for which the Phillies claim credit.

» PHOTOS: Phillie Phanatic through the years

Even if the creators’ copyright claim prevails in court, it would be difficult for another team to use the “free agent” mascot with the same character as the Phanatic, according to experts.

Because the Phanatic is such a well-known mascot, trading him to another team by simply swapping his jersey might lead to violations of trademarks the Phillies hold on the green guy, Kennedy said.

“Let’s be practical here,” he said. "From a trademark standpoint alone, who else is going to want the Phillie Phanatic? He’s as Philadelphia as it gets.”