- "The Sludge Monster from the Earth's Core" redirects here. For the episode, see The Sludge Monster from the Earth's Core (episode).
The Sludge Monster was a large, slimy, purple blob covered in red spots. It had two arms; its left arm was a tentacle and its right arm was stick-thin and had a hook-like hand on it. It had a giant yellow eye with a blue iris located beneath its mouth, which was jagged and contained a long tongue. Though the monster had feet, they were usually concealed by its slimy body.
He didn't seem very bright, given that he attempted to squeeze himself through a doggy door, causing him to get stuck.
A Pup Named Scooby-Doo
Shaggy Rogers and Scooby-Doo were watching TV late at night when they saw a news bulletin about a robbery at the Last National Bank. According to the bank's janitor, Mr. Williams, the robbery was committed by a monster; specifically, it was the Sludge Monster from the Earth's Core. This scared the two until they remembered that the bank was all the way downtown, and stopped worrying. However, when Scooby went to go to bed for the night, he found the monster inside his own doghouse, scaring him away.
Shaggy and Scooby summoned the rest of the gang to investigate the haunting of Scooby's doghouse (which is huge and mansion-like on the inside). They split up, and Shaggy and Scooby decided to take a snack break. However, their meal was interrupted by the Sludge Monster, who chased them all around the house until they ditched him by hiding in a suit of armor, where the rest of the gang found them. When Shaggy tried to call the cops, the phone was covered in slime, indicating that the monster had used it.
The gang discovered stolen gold in Scooby's basement, as well as a hole that led to a sewer. They went through the sewer until they found a ladder, which brought them to the inside of the bank's vault. When they walked out of the vault, the monster entered the bank and came after them. He chased them through the sewers until they got back to Scooby's basement and boarded the hole leading to the sewer.
When the monster eventually broke the boards, he found a trail of gold. The gang had planted it in order to lure him into a trap. They lured him outside of the doghouse, where Shaggy and Scooby planned to spray him with a hose. However, Shaggy turned it on too high, and Scooby lost control of the hose, causing the trap to fail.
The monster chased the gang into the Rogers' house. When they came back out, they opted to use Scooby's doggy door. The monster made the mistake of attempting to use it as well; he got stuck, because it was too small for him. The monster was revealed to be Mr. Buckston, the bank president. He used the disguise to rob his own bank and tried to pin the whole crime on Mr. Williams. He haunted Scooby's doghouse in order to scare Scooby away so he could use it as a hideout.