a fanciful idea的用法和样例：
- He had a fanciful idea about crossing the Pacific in a barrel.
- That would have been a very fanciful idea.
- An unrealistic idea or notion; a fancy.
- A fanciful account that embellishes the true story.
- I have a fancy (ie a vague idea) that he will be late.
- A riddle in which a fanciful question is answered by a pun.