White is a regular cast member on the TV Land sitcom, while fellow "MTMS" veteran Georgia Engel plays a recurring role.
Moore, Leachman and Harper will guest star on an episode of the show, which is set to shoot April 5, Deadline said. The actresses are to play former bowling buddies who reunite years after an epic falling-out.
No air date has been confirmed.
Harper, 73, recently announced she has been diagnosed with terminal brain cancer and is only expected to live for a few more months.