what is your problem/ what is wrong with you ?

Also, it's important to be aware that it's a colloquial, informal sentence. Don't use it if you are talking to people at work or people you pay respect to

It is a simple idiom, which means : hey, are you crazy ? or hey, what's wrong with you ? Let you are having a breakfast with your friend and after sometime, your friend starts behaving like a stranger, you would say "hey, are you crazy ?" or "what's the deal ?". I think it'd help.

If it is a talk show, perhaps they were playing with the words to make them have double meaning at the same time... deal can also mean an agreement of some sort to deal with something, means what you handle So it could have double meaning within the idiom But I certainly agree with the other answers What's your deal bro? would mean what's your problem. Hopefully my added explanation can help you solve the mystery of the strange questions...haha good luck!

"How are you?" or "What's your gain? / Why are you in this matter?"