Martin Sheen, who plays the president on NBC’s “The West Wing,” has asked Bill Clinton, who plays the president at 1600 Pennsylvania Ave., for help in an environmental case. Sheen wants Clinton to close the Waste Technologies Inc. toxic waste incinerator in East Liverpool, Ohio, before Clinton leaves his real-life office on Jan. 20. “Stopping WTI once and for all is the best way to protect the children,” the activist actor wrote in a letter to the Prez obtained by the Associated Press. Members of some 23 state and national environmental organizations also signed the missive.