Who owns 'Happy Birthday'?

Most people have been singing "Happy Birthday" since they were kids. But if you've done so publicly, you could owe hundreds of thousands of dollars in copyright infringement fees.

The song was written more than 120 years ago by Mildred and Patty Hill. Warner Music Group eventually bought the company that owned the rights, and since then, it has been collecting fees.

But now there's a lawsuit that could change that, a documentary company filed a lawsuit on Thursday to have the song returned to the public domain.

Everyone from babes to bombshells has sung the song - Marylin Monroe famously sang her rendition to President John F. Kennedy.

But if it is sung at too public of an event, and without permission, it could cost singers $150,000. That would be € 112,630 for those who once dared to sing to former Pope Benedict.

That six-figure sum is the cost for the unauthorized use of those 16 little words, according to Warner/Chappell music, which claims it owns the rights to "Happy Birthday."

"It's a case in which, I think, the previous owners of the song, the predecessors of Warner/Chappell, at some point didn't think themselves was protected by copyright. But then maybe they saw an opportunity," Robert Brauneis, a professor at George Washington University and legal expert on copyright issues surrounding "Happy Birthday."

If the documentary company’s lawsuit is successful, Warner/Chappell would be out the $2 million it earns every year on the song.

"The arrangements are certainly still under protection, but nobody plays those particular piano arrangements when they perform "Happy Birthday," so that's not economically significant," said Brauneis.

The costly fee is why so many television shows and movies don’t do "Happy Birthday."

Everyone from "The Three Stooges," to "2 Broke Girls" - who would be even more broke if they didn't sing the alternative version on the show - to Mr. Rogers, have gone to great lengths to not sing it.

CNN reached out to music company Warner/Chappell, but a spokesman for the company declined to comment on the lawsuit.