The Cavern was first mentioned in the episode "Bart Vs. Lisa Vs. the third grade" when Bart said "she (Lisa) wet herself at Carl's dad caverns". The Simpson family once visited the caverns. When Bart realized it's a nature walk, he tried to escape. Lisa gave him a nickel in a water bottle to entertain himself and it worked. Meanwhile Homer tried to chip a piece of a long stalactite. However, the stalactite fell into the ground and the family followed it, with Homer getting stunk in the hole.
While Marge, Bart and Maggie were looking for the way out, Lisa told him a story. During talking, it showed up that there are gold coins hidden in the cave. They eventually found the bag with the coins, but suddenly, Rich Texan, Mr. Burns, Moe and Snake with his son Jeremy appeared, ready to fight and have the coins. Marge then grabbed the bag and dropped it down a deep pit. Everyone then realized how greedy they had been and went out to volunteer as a way of atoning for their sins. Except Mr. Burns, who attempted to climb down to get the gold.
Behind the Laughter
The name is a butt on the Carlsbad Caverns.