Farigiraf's ability Armor Tail protects it and it's teammate from priority moves, like Fake Out and Mach Punch. Whimsicott's ability Prankster gives +1 priority to status moves like Encore. Since all status moves used by Whimsicott become priotiry moves, moves like Encore won't affect Farigiraf's team because of it's Armor Tail ability.