U S Attorney Mary Beth Buchanan's office says the goal of it and another device called Number 1 was to help people pass drug tests.
The duo face up to eight years in prison and a $500,000 (Ģ334,000) fine.
They owned the California-based internet company Puck Technology and the devices were sold from 2005 to 2008.
The device, which came with its own heating and Yellow River urine packs, was sold on the internet.
Wills, 65, and Catalano, 62, both from California, face sentencing on February 20, the Post-Gazette said.
"The Whizzinator is the ultimate solution for a drug testing device," says a statement on the website of the California-based company, which calls itself the "undisputed leader in synthetic urine."
"The prosthetic penis is very realistic and concealing is simple, while our quality production and materials assures you that the Whizzinator will let it flow again and again, anytime, anywhere you need it!"
Mr Catalano and Mr Wills pleaded guilty to conspiracy to sell drug paraphernalia and conspiracy to defraud the United States government.
Puck Technology also pleaded guilty to the same charges. The company has stopped operating.
Back in February 2006, a couple figured in a bizarre incident that resulted in a fake penis being microwaved at a GetGo convenience store.
Leslye Creighton, 41, of Wilkinsburg, and Vincent Bostic, 31, of Pittsburgh, were both cited for criminal mischief and disorderly conduct.
Each charge carried a possible sentence of up to 90 days in jail and up to a $300 fine.
Mr. Bostic had filled a fake penis with his urine that Ms. Creighton, a friend, planned to use to pass a drug test she was taking to get a job, Police Chief Joseph Pero said.
Ms. Creighton asked a store clerk to microwave the device so the urine inside would be body-temperature and fool those giving the drug test, Chief Pero said.