Why, Dinah, what makes you think she should?
5 seconds sound clip from the The Philadelphia Story movie soundboard.
You can hear this line at 01:26:07 in the Blu-ray version of the movie.
Quote context
[...]
- Oh, nothing. Nothing much. My head just fell off, that's all.
- What is all this gibberish about Mr. Connor?
- What makes you suspect what, and since when?
- Last night and well into the morning.
- Uncle Willie, isn't it my duty to tell George?
- He might want to marry her anyway.
- But she can't! If she marries anyone, it's just got to be Mr. Connor.
- Why, Dinah, what makes you think she should?
- Apparently the little cherub has heard or seen something.
- I must say, you have a certain amount of cheek, walking in here on this of all mornings.
- Do I?
- Yes.
- What's all this about Mr. Connor, Dinah?
[...]