Robot Fists are a type of weapon which Sparks Nevada possesses. They are antiques, and a very rare item.
The fists can be worn without being powered on, but once powered on cannot be removed without being powered down. The robot powers do not function without being powered on.
Sparks Nevada often uses the fists to disarm or disable his enemies non-fatally. He does not wear the fists all of the time, nor are they his "usual" hands, but a separate item he only wears when necessary.
The robot fists have several known functions. They give Sparks Nevada extra reach, they can be used to take objects, usually weapons, out of an enemy's hand, and can be used to assist with computer usage like hacking. Mostly, however, they allow the person wearing them to punch very hard.
Robot Fists were originally invented by Nikolai Nikola in order to knead bread dough. He wrote the original schematics on a napkin, which was then stolen by Alvina T. Ardison. Ardison swallowed the napkin after memorizing the schematics, then went on to produce the robot fists and sell them as weapons, earning millions for her stolen invention.
Sparks Nevada's pair of Robot Fists were given to him by his father, Captain Caiaphas Nevada, upon his graduation from USSA Space Academy. Mercy Laredo persuaded Caiaphas to allow Sparks to graduate by promising to punch him in the nose every day until he agreed. Mercy claims Caiaphas gave Sparks the fists as a reminder of how little he wished to be punched in the nose again.
Real-World Robot Fists
A pair of real Robot Fists were an offering for The Thrilling Adventure Hour Kickstarter.
These fists are non-functional as far as having actual robot parts, but can be worn. They were designed and made by Paul Pape.
Although Sparks Nevada typically has his robot fists with him most of the time he is working, they factor heavily into the following episodes.