Who is the main actor in the "Pirates of the Caribbean: At World's End" movie?
main actor refers to person_name where Min(cast_order); "Pirates of the Caribbean: At World's End" refers to title = 'Pirates of the Caribbean: At World''s End'
SELECT T3.person_name FROM movie AS T1 INNER JOIN movie_cast AS T2 ON T1.movie_id = T2.movie_id INNER JOIN person AS T3 ON T2.person_id = T3.person_id WHERE T1.title LIKE 'Pirates of the Caribbean: At World%s End' ORDER BY T2.cast_order LIMIT 1