“Beware of Dog” is episode fourteen of season two of Farscape.
After learning that organic goods from the system they have just done business with are often infested by parasites, Chiana and D’Argo return with what is known as a Vorc to kill them. The parasites are apparently very dangerous – and rather large. These aren’t minuscule bugs by any stretch of the imagination. They’re far too big to even step on. The thing that hunts them is an ugly looking creature too (it looks like one of the Gremlins from the films).
Crichton thinks he saw one of the parasites, but Aeryn thinks that Crichton is losing it. Which may be true, as he’s seeing Scorpius around the ship. The Vorc isn’t helping, as it keeps running away.
There’s a quote rather similar to one in Aliens – ‘What do you expect me to use? A harsh language?’