Doctor Demento is a sadistic dentist that operates on Rocko's mouth. During the procedure to extract Rocko's rotten tooth, the machine explodes since Demento has a lit match nearby, causing both Rocko and Demento to be hospitalized.
A letter to the editor printed in Issue #3 written by Joey Marchese of Union, New Jersey described Demento as "spoofed" by Mike Lackey and Rick Parker from the dentist in the first issue of Marvel Comics' Beavis and Butt-head. Mike Lackey responded, describing the similarities as "the strangest of coincidences, perhaps completely the work of planetary alignment or the magnetic resonance of the earth, or maybe the eclipse... Yeah! The eclipse!" He then continued, "ROCKO editor World Famous Mike Lackey looked directly into the sun while shuffling scripts, and...! Yeah, yeah, we don't buy it either!"
The character has no relation to the radio host of the same name.