Rincewind glances down at the Octagon. "It doesn't have any special properties. You just wear it so people know." He doesn't understand why this is so difficult to understand. "And anyway, duplicating it would be just as dangerous as impersonating a wizard." Not to mention that he hasn't the faintest idea how to go about duplicating anything.
"It certainly does exist," Rincewind insists stoutly. "It's the premier collage of wizardry on the Disc." He crosses his arms and delivers his crushing blow. "I've never heard of Hogwarts. Can't say I'm terribly impressed. What kind of school is named after a nobbly pig?" That slight breeze you feel is the Universe holding it's breath at Rincwind's amazing capacity for putting his foot in his mouth and right down his throat and (quite possibly) out the other end.
Rincewind sighs. He's going to end up on the menu no matter what he does. "All right," he says hopelessly. "But I did warn you." He reaches into his robe and pulls out a slender white stick. With a furtive glance at the kitchen and a silent prayer to any and all gods that might be anywhere in the area, he waves it tentatively. Immediately the table is covered with pumpkins. They roll off the table and onto the floor. The drinks and bread are crushed under the orange onslaught. Rincewind just sits there, a smallish specimen in his lap and an 'I hope you're satisfied' look on his face.