The Proteans (also called Protys) are a race of shape-shifting aliens from Antares 2 who look like fluffy goo. Originally they were thought to be of limited intelligence.
The first know member was Proty, who was taken as pet by Chameleon Boy. But after the death and resurrection of Lighting Lad, the legionnaires discovered than Proty was far more intelligent than they believed.
In the 5YL continuity, Glorith tried to subjugate the Proteans but was stopped by the plan of seven Proteans. These seven removed the sentience of the other members of the Protean race and created the Soul of Antares. This soul of Antares was then given to a Protean who was given the false identity of James Cullen. The Proteans gave him a belt that granted him stasis powers and with the assistance of R.J. Brande placed him with the Legion of Super-Heroes as Kid Quantum to hide the soul from Glorith. Later Kid Quantum would fake his death to leave the team and he went into hiding.
The Legionnaires later helped Kid Quantum use the Soul of Antares to restore sentience to the rest of the Protean race. As a boon the Proteans changed the Protean that was James into a flesh and blood human and gave him the stasis powers as a metahuman ability that he once had access to via his stasis belt.
In the post-Zero hour Legion, the proteans didn't appeared to have major cognositive capabilities.