An unassuming gray PolyPortables Inc. restroom has struck a chord with musicians and achieved backstage celebrity status at the annual Country Fever music festival in Pryor, Okla.

And no one’s happier about it than Tammy and Stacey Hillis, the president and general manager, respectively, of At Your Service, a portable sanitation business in nearby Tulsa that services the huge music celebration. Bringing new meaning to the words “signature service,” the restroom is covered with 75 to 100 autographs of musicians who’ve played at the country music extravaganza for the last three years, reports Tammy Hillis.

“Stacey came up with the idea — he’s always thinking outside the box,” Hillis relates. “He really likes the singer Thomas Martinez, so three years ago, he asked him to autograph the restroom. He thought it would be fun.”

Martinez agreed, and the rest is star-studded history. The restroom, which has become a backstage fixture at the concert festival, has now been autographed by luminaries including Willie Nelson, Trace Adkins, Montgomery Gentry, Shenandoah, Lonestar, Trick Pony and the Oak Ridge Boys.

“People backstage look for it now,” Hillis notes. “We forgot to bring it this year, and they called us and asked us, ‘Where is your signature toilet?’ So we had to bring it on out.”

Initially, musicians either loved the idea or hesitated a bit before signing it. Now, some artists want to sign it before anyone even asks them. Only one singer, Carrie Underwood, has declined to autograph the restroom, Hillis notes.

“Her manager wouldn’t let her sign it,” Hillis explains.

So what does At Your Service plan to do for an encore when the restroom is covered entirely?

“I guess we’ll start another one,” Hillis says.