Felix Leech was a thug and assistant to the gangster Cyrus Redblock in the Dixon Hill series. He was well known to Starfleet historian Whalen.

In 2364, when the USS Enterprise-D's holodecks were malfunctioning, the senior staff was held at gunpoint by a hologram of Felix Leech. Leech shot the historian Whalen. Subsequently, Leech was forcibly removed from Dixon Hill's office by Captain Picard who struck him about the face. He returned with the hologram of Cyrus Redblock who seemed to take offense at the Captain's abuse of Leech. When the holodecks were restored, both Leech and Redblock attempted to exit, but were immediately dematerialized. (TNG: "The Big Goodbye")

Felix Leech was played by actor Harvey Jason.
He was described in the script as a man with "short curly hair and big bulging eyes. He wears a bow tie and speaks with a strange nasally tone that betrays a Middle-Eastern background." [1]
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