But, those Canada=cold jokes are so funny...
If you'll consider waitresses as performance artists for a moment, this is the stupidest/funniest question anyone ever asked me:
During a convention at the hotel across the street, the modest "Irish" pub I work(ed) in was jam packed. This convention boasted some particularly annoying and needy attendees, so everyone's temper was a bit short. A man asked me for a Chardonnay, but whemn I brought it back to the table he said he had ordered a red wine. "I'm sorry, sir," I said, "but I'm pretty sure that you ordered a Chardonnay." "Yes," he replied, "but I wanted a RED Chardonnay." I was a little irritated, but I'm no wine expert myself so I brought him a "red Chardonnay" (a burgundy) and asked if they were ready to order. He said they were, but he had one question first: "What type of fish do y'all use in your New York strip?" (this while pointing at the section of the menu clearly labelled STEAKS AND CHOPS)
Second runner up, when I worked at a very busy Starbucks (briefly) a woman asked me if she could set her medium sized dog on the counter while she looked for change. People at Starbucks also often inquired, "Do you sell coffee?"