This expression expresses the feeling of "I can't believe this is happening to me!" that you feel when something annoying or inconvenient happens to you.
For example, you can say or think "You've got to be kidding me!" in the following situations:
- Your boss has sent you an email asking you to come in to do some extra work this weekend.
- You drove to the gym to exercise, but when you get there you realize that you didn't bring your gym shorts.
- You go into a clothing store. When you check the price on one of the store's t-shirts, you see that it's $150.
The word "kidding" means "joking with". The original meaning of this phrase is "This must be a joke. It can't be true."
You might wonder who "you" in this phrase refers to. It means the person who did the annoying or surprising thing. For example, if you see something really expensive, you can say this to your friend:
Fifty dollars for a pair of socks? You've got to be kidding me!
"You" means the store, the designer, or the person who set that high price.