You Can't Scare Me!
According to Muddy Creek legend, a long time ago, there were two neighboring villages: one village was poor and lived in the forest, and the other was more wealthy and well established. The city village hated the forest village and treated the villagers from the forest village poorly. One stormy night, a rainstorm caused the creek in the forest to overflow and flash flood, burying the entire forest village in a mudslide killing all the villagers. Local legend claims that once a year, the townspeople return to form covered in mud and go to find innocent victims to drag back with them into the mud.
Eddie, Hat, Molly, and Charlene hide about 100 yards behind Courtney's tree house and they see her looking out into the creek with binoculars. Suddenly, behind her, three shadowy figures emerge. Eddie's brother and friends came through....their plan worked! Eddie hears rustling behind him and the friends turn to see three more mud monsters! Eddie's brother apologizes for being late. The group turns back towards the tree house and sees dozens of mud creatures emerging from the ground, all advancing on Courtney and the tree house. They scream and yell until she notices, and all of them make a mad dash run out of the forest, escaping the mud creatures.
In addition to their appearance in You Can't Scare Me! and its accompanying television adaption, the Mud Monsters appear in the book The Knight in Screaming Armor from the Give Yourself Goosebumps series.