In " Four-Eyed Jack," Grandpa tells the kids the story of a previous boarding house resident who used to do experiments in the basement until he died in an explosion. Now he supposedly haaaaaunts the boarding house until he finds his missing glaaaaasses. Arnold investigates the basement, only to find that Grandpa told them that story so he could take dank shits in private (that's reasonable). Later, we see the ghost of Four-Eyed Jack take his glasses back from a sleeping Arnold and try to tuck Gerald in, only for him to wake up screaming. Then it ends. That's it. Thanks for watching, children. Now stay tuned for The Angry Beavers!
"I've been watching you sleep for yeeeeeeears."
This happens constantly. An episode will end in a Scooby-Doo reversal, only to re-reverse back to the supernatural being real. In another episode, Grandpa tells the kids a story about a haunted train. The legend is debunked, but afterwards, a real ghost train is seen flying off the tracks by one of the characters.