Special Somepony
Very Special Somepony, or just Special Somepony is a term among Ponies for a boyfriend or girlfriend, if not a spouse as well.
Overview
During Hearts and Hooves Day, the Cutie Mark Crusaders attempted to find Miss Cheerilee a "Very Special Somepony" to spend her day with, eventually settling on Big McIntosh a their choice for her.[1]
Clear Sky referred to Quibble Pants as her 'special somepony', meaning the term isn't exclusively used by foals.[2]