This is one of the more random Hollywood fights that I can remember, but apparently Michelle Trachtenberg is fighting with Jonah Hill because he was a d*ck to her years ago. The two got into it last week at Charlotte Ronson's birthday party in New York.
From the New York Daily News:
Around 1 a.m., Hill approached a gaggle of girls that included [Michelle Trachtenberg] on the roof-deck of the Bowery Hotel to say goodbye to one lady in particular. Trachtenberg "told him they had met at Saturday Night Live a while back, but [at the time] Jonah would only talk to Blake Lively. She accused him of being rude to her, and said she had told her mom about it," recalls the guest.
But the "21 Jump Street" star wasn't biting: The source says Hill looked directly at Trachtenberg and responded, "I don't know you." The 26-year-old brunette then "awkwardly ended the conversation" and headed toward the steps with a male companion.