Bubble Creatures
The Bubble Creatures were a spacefaring non-humanoid species, the first aliens encountered by the Robinsons after leaving Earth. When Will Robinson made first contact (in a strange padded chamber inside the Derelict spaceship), their apparent means of speaking was an electric arc in the "facial" region, but they apparently were aware that Will was making audible sounds. The aliens did not threaten Will, suggesting that no hostility was offered by the aliens. Relations quickly soured after Dr. Smith shot one of them. ("The Derelict")
Second Appearance
In the second season episode, 'Prisoners of Space', one of the bubble creatures appears (although only in silouette for much of the episode). Strangely (probably due to a writer's oversight) the creature does not spark but talks plain english. We learn that when Will entered the padded chamber he automatically activated the suspended animation system which awoke the creatures.
Later in the episode, the Bubble Creature (the main judge presiding over the Robinson's trial) reveals himself to Dr Smith.
Background
These aliens were never referred to by name but are listed with this nickname in the Internet Movie Database.[1] The creatures were portrayed by Dawson Palmer in an uncredited role.