You May Have Missed This Detail In Last Week's "Game Of Thrones"
Dothraki never forget a face.
If you saw last week's Game of Thrones, you saw Jorah's master plan to save Daenerys go into action.

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But that plan crashed and burned pretty quickly when this Dothraki soldier called them out.

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Later, we learn that his name was Aggo, and he was part of Khal Moro's khalasar.

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Who cares, right? WELL. As Redditor NANAs_Mic points out, Aggo was the name of one of Dany's men back in Season 2.

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Back in Season 2, Episode 1, Daenerys sent out three riders when they were wandering the Red Wastes. Rakharo got killed, and Kovarro came back with an invitation to Qarth.
Aggo here NEVER CAME BACK.

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So it seems as though Aggo betrayed his own Khaleesi and defected to Khal Moro's horde.
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Of course, there's the possibility that there's more than one Aggo. After all, they do look different...but then again, so does Daario.
That would explain why he knew for a fact that Jorah and Daario weren't merchants; he recognized Jorah's baby blues from back in the day.

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Guess he got what was coming to him.

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