Good question! They are both single-mindedly in pursuit of something (Montresor about killing his foe, Fortunato about the amontillado), they are about the same age, from the story and the language they use it seems they are from similar backgrounds. They have many of the same interests, including, but not limited to, their love of fine wines. They both love a good party, and perhaps a good joke. Fortunato obviously believes up until the last horrifying moment that Montresor is kidding around as he handcuffs Fortunato to the wall and begins to brick him into the wall itself. They are both arrogant--Fortunato about his knowledge and expertise of fine wines; Montresor about the ills done to him by his greatest foe, Fortunato.
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