I usually make an ass of myself. Just recently I remembered how frequently I do this specially in restaurants. The following three conversations actually happened to me, and yes I am not proud of it :S
In a fancy beer garden in Berlin
Me: Can I have a Heineken?
Disgusted waiter: No sir, we offer a fine collection of German beers.
In a refined Italian restaurant in London after my classic pizza arrived
Me: Can I have some Ketchup?
Disgusted waiter: We don't have Ketchup here.
In a Greek restaurant
Me: Can I have one Kebab pls.
(Kebab is the Turkish name of a meat sandwich)
Disgusted waiter: You mean Gyros?
(Gyros is the Greek name of the same sandwich)
Me: Yes, one Greek Kebab pls.