CREATE TABLE table_16568 ("Character" TEXT, "Portrayed by" TEXT, "Relationship" TEXT, "First appearance" TEXT, "Last appearance" TEXT)

What episode was the last appearance of the character, rikki sandoval?
SELECT "Last appearance" FROM table_16568 WHERE "Character" = 'Rikki Sandoval'
SELECT "Last appearance" FROM "table_16568" WHERE "Character" = 'Rikki Sandoval'