In "Ice," a clear X-Files homage to John Carpenter's The Thing, Mulder and Scully head to a remote Arctic research station to investigate unexplained goings-on with the scientists working there, only to encounter a species of parasitic worm that gets under one's skin, literally. Like the black oil, the "Ice" worm creature is theorized to be of alien origin, landing on Earth via a meteor. Also, like the black oil, the "Ice" worm is able to manipulate and control the behavior of its host, although not quite to the same extent. In "Ice," the worms' manipulation abilities are more about causing disorientation, paranoia, and confusion in its host, while the black oil completely takes over their will.
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Most tellingly of all though, when a parasitic worm is forcibly extracted from its host, it squirts out a black, oil-like substance. Considering the black oil's ability to control life forms, the most likely possibility here is that the species of parasitic worm encountered the black oil at some point in the distant past, and was subsequently taken over by it fully. So basically, the worms were parasites before they met the black oil, but exposure to the black oil effectively enhanced them, making them more of a threat. Those involved with making The X-Files have yet to confirm or deny this possible connection.
Via: Screen Rant