The stars reportedly got into a heated exchange backstage at Alexa Chung's MTV talk show on 6 August (09) after the former Saturday Night Live star made a joke about Piven's alleged bout of mercury poisoning, which was the reason he gave for pulling out of the play Speed The Plow in December (08).
Kattan reportedly greeted Piven by quipping, "So, what are you here to promote, your Broadway play?.
The Entourage star was said to have shot back, "Well, what are you here to promote? Mango?" in reference to Kattan's SNL stripper character.
Piven's spokesperson acknowledges the pair met - but insists reports they shouted at one another are completely fabricated.
The rep tells RadarOnline.com, "Jeremy and Chris did see each other at MTV and they were joking around backstage before a talk show appearance, as people often do. If it was interpreted as a fight, someone wasn't paying attention, that's all. Both gentlemen spoke on the phone yesterday, there is no issue.".