Mischa Barton's Halloween horror

(BANG) -

Mischa Barton sparked a fight at a Halloween party.

The former 'O.C.' star was left furious when a reveler threw a drink over her at New York's Park Bar on Saturday (31.10.09) after she accidentally stepped on his foot, throwing her own beverage at the unnamed partygoer in retaliation.

An onlooker said: "I was standing beside this guy at the bar when Mischa went past us carrying two drinks.

"The next thing I knew he threw his drink over her back and she turned around and asked him: 'Did you just throw a drink over me?'

"The man responded that the drink was in retaliation for Mischa stepping on his shoe and she threw one of her drinks in his face."

The incident took an ugly turn when the actress - who was dressed as a peacock - returned to her table and told her friends, who rushed to confront the man.

The source added to Radar Online: "Within a few minutes one of her male friends came over to confront the guy and asked him to step outside. Mischa's friend left but then he kept coming back every few minutes to complain."

The two men then allegedly fought on the dance floor before two bouncers came and threw out the instigator - who had "a gash to his head and his knee was all cut up".