Cromulon

The Cromulons are a species of planet-sized entities appearing as giant heads which, according to Rick Sanchez, feed on the musical talent of other species. When a Cromulon travels to Earth seeking the musical talent of the Human race, it was seemingly satisfied when Sanchez, along with his grandson Morty Smith, performed "Get Schwifty". However, this lead to Earth itself being abducted and involuntarily forced into competing in "Planet Music", a reality show hosted by the Cromulons in which several species compete in a musical competition. The planets of those eliminated from the contest, or simply refused to perform, are destroyed.

Over the course of this incident, several Humans mistook the Cromulons for gods, creating a cult worshipping them as such and mistaking their comments on Earth as commands.

Biology
The Cromulons are giant, bodiless humanoid heads although while they all appear and sound identically similar from one another. However, skin varies among individuals and includes green, yellow, red, blue, orange and purple. They also speak in a rather deep yet monotone voice.