Where are you if you are in cloud cuckoo land? Answer: a very unrealistic place.
It's what you might say to somebody who is overly optimistic about their chances in a situation.
If you think you will marry a prince, you're living in cloud cuckoo land. Still, it worked for Kate Middleton!
Looking for a suitable video clip for Cloud Cuckoo Land, I came across this song by Takako Minekawa; quite interesting!