Fallon/N.Y. creatives Linus Karlsson and Paul Malmstrom are leaving the agency to join the yet-to-be-launched New York office of U.K. ad agency Mother. At Mother/New York, they join Andrew Deitchman, former global director of marketing communications strategy and business development at WPP Group's Red Cell, who was tapped to head the startup in June. A date for Mother's U.S. launch has not yet been set. ... Director Laurence Thrush has signed with Headquarters for exclusive spot representation in the U.S.