Coal the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to
A Star Is Burns Lovitz, the episode guest stars Maurice LaMarche, a regular on "The Critic", who voices George C. Scott as well as Jay Sherman's belch. Phil Hartman also makes a brief appearance as an actor resembling Charlton Heston portraying Judah Ben-Hur in Mr. Burns' film. Rainier Wolfcastle's line, "on closer inspection, these are loafers", was ad-libbed by Dan Castellaneta who was providing the voice of the character on a temporary track. It was later re-recorded by Wolfcastle's normal voice actor, Harry Shearer. The Imperial March from "The Empire Strikes Back" is played as Mr. Burns is introduced. The song the "Rappin' Rabbis"