According to TMZ Sports "everyone's" favorite irreverent sports blog sight is being sued over possibly their most famous product. Barstool Sports long standing fued with the NFL's front office and commissioner Rodger Goodell is well documented and the light blue shirt with Goodell's likeness wearing a clown nose is a monument to that battle. In 2015 Barstool made the shirt available and now it's one of the images Barstool is known for. One problem the designer of the picture is suing over it's continued use.

The guys behind the suit are Jake Bernier, Kenneth LeMarier and Joseph Bernier ... who claim they created Sad Roger and licensed it to Barstool for a "one-time use in 2015."

In their lawsuit, filed Monday in federal court in New York, the alleged creators claim Barstool never got permission to use the image after that one-time usage license in 2015 ... and they're pissed.

The guys claim they're entitled to $150,000 for every time Barstool infringed on their copyright -- though they haven't specified exactly how much money they want from the suit.

Barstool posted the full conversation they had with the guy on their site and Dave Portnoy's response.