Who was the actor who was portraying "Alex Brown" and has been credited?
who refers to name; portraying "Alex Brown" refers to role = 'Alex Brown'; has been credited refers to credited = 'true'
SELECT T1.name FROM Person AS T1 INNER JOIN Credit AS T2 ON T1.person_id = T2.person_id WHERE T2.role = 'Alex Brown' AND T2.credited = 'true'