He is first introduced in episode 2, when he attacks Hitomi. The english and Japanese versions have different interpretations of what happens during the scene where he attacks her; in English Hitomi later refers to him as "It's that theif from before!" whereas in Japanese, Hitomi labels him as a pervert indicating that the scene was meant to have more rapeful connotations. Of course, it's all clarified through his explanation later: he was after the pendant, not the... anyway.
Moleman appears numerous times later. In ep 7, drunken aboard the ship with Millerna, in ep 8 when Allen is injured, in ep 9 when he eavesdrops on Millerna and Allen.
So why is he the most aware/smartest character?
Moleman watches and takes in everything. There is no doubting, no second guessing with him, he sees things, analyses them, remembers them. He is also extraordinarily helpful. In ep 2, he returns to Hitomi her duffel bag and leads Van to the Escaflowne. In ep 3 Van uses his knowledge of Barr leaves to remove the poison from Merle and Hitomi's wounds. In ep 8, he has retrieved Millerna's bag before she even asks for it, having acknowledged and listened to the conversations about a wounded man. In ep 9 we see just how he gets his knowledge of what goes around by peering through the doorway at a warm and fuzzy moment between Millerna and Allen. There is enough proof of his usefulness in ep 3, when he is seen on the Crusade with the rest of Allen's crew as they flee Dilandau's wrath. Why would the crew bother to save him, to bring him aboard with them? We can assume he could have easily escaped on his own, but the fact that he was pulled along asserts that he was valuable, for backdoors and information most likely.
My favorite scene with the Moleman occurs in a scene that was actually removed from the cut version and can be found only on the uncut version. In ep 20 (roughly the equivalent of 16 cut) Millerna is preparing for the wedding and is searching for a particular necklace to match her gown. In her search she notices her table move and beneath it is none other than the moleman, who had disappeared for a few eps. He pops out, the necklace in hand, and ties it around her neck.
"Out of all the treasures you have, there is only one that perfectly suits you," he says, and pauses slyly. "Know what I mean?"
The allusion is of Millerna's uncertainty, and it's unsure if even Millerna recognizes the reference. I admire him for being able to say what others were unable to.
In Escaflowne: a girl in Gaia, the Moleman is a prophet. I found this to be a greatly appropriate choice.