“Exodus from Genesis” is episode three (possibly) of season one of Farscape.
Whilst hiding from a Peacekeeper ship behind a debris cloud, some of whatever the cloud is composed of gets inside Moya. Which turns out to be rather large bugs of some description.
Aeryn says that she can’t think of anything she could possibly want Crichton for – and such a straight line is going to get a response. Especially when the bugs start creating replicas of the crew members in order to take over the ship, and the ship gets hotter and Aeryn starts to overheat and lose her mind as a consequence (Peacekeepers have problems with heat; a way in which they differ from humans).
The bugs remind me of the Skitters from Red Dwarf. Although perhaps not as user-friendly.
Another episode where the exact number isn’t known. Depending on the source, it’s either episode two, three or five.