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What about this guy?

I believe the above sentence is correct. Why doesn't it have the usual interrogative sentence structure like the following ones?

Where were you?
What are you doing?
How do you do?
How did you do that?
How could I do that?
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It's correct, but it's not a sentence. It has no verb.

It is an idiomatic expression that can stand alone, like Yes, No, Maybe, Please, Not now, Not on Tuesdays, In the kitchen, As soon as you can, Whenever you want, and thousands of other sentence fragments commonly used in conversation.

CJ

For more on "How about...?" and "What about ...?", see what about...?.
Comments  
Students: We have free audio pronunciation exercises.
Hi Jim

A Merry Christmas and a Happy New Year. You have always helped in a very good way. I owe you a lot. I wish you and loved ones good health and many years of happiness.

Best wishes
Jackson
Thank you, Jackson. And Merry Christmas and Happy New Year to you, as well.

Jim