Xenomorph

A facehugger was a fictional alien lifeform which appeared in the horror movie simply titled Alien. Professor Albert Smithe noted a resemblance between the dream crabs' method of consuming their victims' brains, by latching onto their face, and the facehuggers. (TV: Last Christmas)

When Bernice Summerfield visited Ace in hospital, she thought that the respirator clung to her like a facehugger. (PROSE: The Left-Handed Hummingbird)

Behind the scenes
In the real world Alien franchise, the Facehuggers are part of the early life-cycle of the Xenomorph.

Interestingly, while the Alien movies exist within the DWU, there has been no explicit connection in valid or invalid sources to draw the Xenomorphs specifically to the series - that is to say, Xenomorphs are consistently portrayed as real entities that reside in the DWU. It should be noted though, that PROSE: The Annotated Autopsy of Agent A does, albeit with names changed for copyright concerns, that the "life-spores" (a thinly veiled version of the Xenomorphs) were an aspect of the Enemy, and that the Enemy essentially inserted the "life-spores" in Earth's popular culture, explaining how Xenomorphs could be both real and fictional.

While TV: Last Christmas does confirm that the Facehuggers are from the Alien series, PROSE: The Left-Handed Hummingbird is more ambiguous.