Jeremy Piven could still be feeling the effects of his reported sushi-induced mercury poisoning, assuming the symptoms include sensitivity to teasing and fits of rage. The New York Daily News reports the "Entourage" star got into a "screaming match" backstage with Chris Kattan during an appearance last Thursday on MTV's "It's On With Alexa Chung." Seems Kattan made the mistake of asking Piven if he was there to promote his Broadway show "Speed-the-Plow," which he bailed out of in December because of the ostensible mercury overload. Jeremy fired back, "Well, what are you here to promote? Mango?" More heated words were exchanged, says a source, and then, "Jeremy said something really personal to Chris that basically attacked his career. He said, 'Whoa, man -- I thought we were just fooling around here.'" Piven not-so-calmly explained that he was "getting sued for that [bleep]! It's not funny!" before supposedly slamming the door of the green room in Kattan's face and bellowing obscenities. About 15 minutes later, Chris tried to offer a mea culpa but was met with another door slam in the face. The official word from Piven's rep (via 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." Kattan's mouthpiece offers a slightly different version, telling the paper, "Chris mistakenly asked Jeremy if he was there to promote his play and Piven fired back with, 'What are you here to promote, Mango?' Chris tried to apologize."