that's a good question 

A phrase usually indicating that the speaker has absolutely no idea how to answer said question. Often used to stall for time.

Photography teacher walking in on students who should be at pep rally: What are you doing here?
Sreya: That's a good question!

that's a good question by Shen June 28, 2004

That’s a really good question 

Something I say a lot when I don’t know the answer to a question.

Person: what’s your favorite color
Me: that’s a really good question

That’s a really good question by Hbfggsz October 11, 2023

thats a good question 

i don't know the answer

larry king: "how do we get iran to disarm their nukes without invading?"

guest politician: "thats a good question larry"

thats a good question by stg60913b September 18, 2010