The Observers are an alien race who claim they are hyperintelligent, psychic, and all confusingly share the name "Observer". The race also claims to be without bodies (despite obvious evidence to the contrary) and carry their bright-blue brains in large Petri Dishes, rather than inside their (supposedly nonexistent) skulls.
They all claim to be omniscient and omnipotent, much like Q from Star Trek and his people, but they frequently fail to demonstrate these supposed abilities. In one of their earlier appearances, the one that later came to be known as Brain Guy by the other Mads, had tested the rest of the cast to see if any of them are deserving of the right to become part of their kind. He was surprised when Tom Servo scored higher than even him, which led to his being painfully punished.
In time, the survivors were able to reconstitute their planet (as stated in Experiment 904 The Deadly Bees). Observers 1 & 2 tracked Brain Guy through time and space to Castle Forrester, where they attempted to take him back to their planet and blow up the Earth as they left. Brain Guy initially agreed, but later changed his mind and (with the help of Pearl and Bobo) separated his former comrades from their brains. He then changed them into Wisconsinites and sent them off to a life of cheering for the Green Bay Packers.
The Observers make a return during Kinga Forrester's experiment on Jonah Heston, specifically to oversee the wedding of Jonah and Kinga (which completely fails to come off due to Jonah's apparent death at the hands of Max).