Diagnostic Repair Drones or DRDs are small robots that move around Leviathans. They are built by the Leviathan as it grows. The DRDs are extensions of the Leviathans consciousness when the Pilot is not in control of them. Because of this, DRDs can be used by crew members to communicate directly with a Leviathan, should the Pilot be incapacitated. The DRDs perform various functions including ship repairs, searching for lost items, and defensive combat using built-in lasers.
DRDs are ovoid, approximately 14 inches long, 10 inches wide and 8 inches tall, with two flexible black eyestalks with lights. They contain multiple tools and sensors to maintain and repair the Leviathan they inhabit, including a plasma welder which can double as a weapon.
One of the indispensable tools they carry contain translator microbes which made communication between all members of the ship (and other ships) possible. One of the DRDs in the very first episode injects these microbes into Crichton's heel shortly after his arrival on Moya.
The most notable DRDs are 1812, a DRD painted blue, white, and red, and named for the "1812 Overture" which John Crichton taught it to "whistle"; DRD "Pike", named after Christopher Pike of Star Trek, who communicated through the use of blinking lights, and sacrificed himself (unintentionally) to destroy an energy rider; and One-Eye, a DRD who surfaced randomly, recognizable by his one broken eyestalk, which was damaged when John arrived, and repaired (badly) with tape by John at the end of his first day out of guilt for breaking it.
There is also a guard type DRD that is used aboard Scarran bases and ships called sentinels. These are not produced by Leviathans and are most likely controlled by a computer. They are armed and can sense weapons that people are carrying, even if they are hidden. If someone has a weapon in a restricted area, they will sound an alarm and/or attack the person with lethal force.
According to Dave Elsey, DRDs are not made from bicycle helmets, and "they are completely pattern made by model makers; they are much bigger than a bicycle helmet!" ("Cool Farscape Facts" - Starburst Edition DVD v3.2)