Wuzzles (1985)

Moosel's wild imagination manages to get him into a lot of trouble while the Wuzzles were picking appleberries. It finally gets so bad that boulder manages crash into the dam. When Moosel is sent home, he suddenly thinks that he's imagining a big monster that keeps following him around. It's actually a real monster with a very bad toothache. When the other Wuzzles see it and convince Moosel that it's a real monster, it offers to help save the leaking dam.