Funny man Robin Williams definitely isn't laughing about this impersonation - he's suing a celebrity impersonator and agent for allegedly conning charities.

The Oscar winner has filed a suit in a Minnesota federal court against his look alike Michael Clayton and his agent Michael Pool, alleging that the pair has "gone to great lengths to dupe innocent members of the media, general public and charitable organizations into falling for their ruse", reports Internet portal Femaefirst.

According to the "Mrs. Doubtfire" star, Clayton and Pool contacted a Missouri woman and arranged for Robin Williams to appear at a fundraiser for the local volunteer fire department.

Clayton allegedly impersonated Williams over the phone to convince her that he was the real actor. The pair reportedly asked for $2,500 to cover expenses. The unnamed woman, who felt suspicious, cancelled the fire department fundraiser, costing the charity in excess of $40,000.

Williams is now seeking an injunction against Clayton and Pool, to stop them from using his "identity, name, likeness and voice without expressly informing his actual and potential audiences that Clayton is not the real Robin Williams".