Fictional character with a famous opening line

ALIBABA

Think of the magical phrase that opens a hidden treasure in a classic Arabian tale.

This clue refers to the character Ali Baba from One Thousand and One Nights, whose famous opening line is "Open Sesame!"—the magical phrase he uses to enter the cave of treasures. The wordplay here is subtle: "opening line" hints at both the first words spoken in a story and the literal act of opening something, like a door. Since Ali Baba is a well-known fictional figure tied to that iconic phrase, the answer fits perfectly.