[Shaggy and Scooby realize what's happening and take off running.]
After running from the skull, Shaggy wishes he had a ham sandwich. A ham sandwich appears right out of nowhere. He then complains that it needs mustard. And then a jar of mustard appears.
Shaggy: This has gotta be my imagination, otherwise, I'd be scared stiff!
Shaggy then asks for his imagination to cut the sandwich in half. The nearby suit of armor drops its ax right onto the sandwich, cutting it perfectly in half. Scooby and Shaggy run away...after which Shaggy returns to pick up the sandwich.
In the episode "Mystery Mask Mix-Up", Shaggy tries pretending to not be scared to keep the masked figure, Zen Tuo, away. How does he do this? He picks up a stick and draws a line on the dirt floor, daring Zen Tuo to cross it. Shaggy does this several times before Zen Tuo finally just takes Shaggy's stick and breaks it.
Also from the same episode, as Shaggy and Scooby escape Zen Tuo, this exchange occurs as they board up a door to hide behind:
The Open Sesame moment in "Go Away, Ghost Ship": A hidden warehouse is guarded by a (mechanical) talking skull that demands a password. Fred tries "Sixteen men on a pirate's chest," which doesn't work; Velma tries "Yo ho ho and blow the man down," which doesn't work either. Shaggy tries "Yum yum yum and a liverwurst à la mode" as a joke and it does.
Shaggy: Wow, some password!
Redbeard turns out to be Genre Savvy enough to realize that Shaggy and Scooby sabotaged a stew they made for him, so he makes them eat it. Fortunately they put soap in it so they spit bubbles at him to escape.
In "A Gaggle of Galloping Ghosts", the vampire tells the gang that they're not welcome in the castle and tells them to leave. Velma tells him to stop that.
During their trip to the fortuneteller, she warns them that they're in danger of "evil forces from the world of the dead" in the mountains. Scooby hides under the table, being afraid of the werewolves.
Shaggy:[angrily] There are no werewolves, Scooby! You get back here!
In "Which Witch Is Which?", after only finding a voodoo doll of Zeb: