Time Cop

Time Cops are a species of Fourth-dimensional creatures whose role is to keep the balance of the space-time continuum. The actual name of the species is unknown, but they're only ever referred to as "Time Cops", so we'll call them that.

Biology
They have heads resembling testicles and long arms ending in standard five-digit hands, but no legs. Instead, they rely on levitation for mobility. According to Rick Sanchez, Time Cops are biologically immortal. After a severe altercation with Rick, one Time Cop was reduced to a liquid splatter, only to evidently make a full recovery shortly afterwards.

Despite their transdimensional nature and immortality, Time Cops are far from omnipotent. When apprehended by a Time Cop, Rick Sanchez distracted him by prompting him to turn around, stating that in his infinite lifespan, he would likely do everything any other person would do at least once, including falling for the ineffective 'there's something behind you' bit. Later, this same Time Cop and one of his fellows physically assaulted Albert Einstein after mistaking him for Rick.

Technology
Little is known about the technology utilised by Time Cops, although they seem to use both mechanical and biological devices. One Time Cop issued Rick Sanchez and his grandchildren with collar-like devices which stabilised the fractured timeline they had accidentally created. He later brandished a slug-like creature he claimed was a weapon capable of regressing the target into an undeveloped fetus. This Time Cop also referred to the creature as 'Chris' and was evidently angered when Rick "killed [his] gun."

Appearance

 * Adventures of Rick & Morty Season 2 Episode 12: A Rickle in Time
 * Adevntures of Rick & Morty Season 4 Episode 4: Rattlestar Ricklactica