What happened to you? or What did it happen to you?

Eladio,

1) What happened to you?

Common and accepted.

2) What it happened to you?

I am not sure that it is grammatically correct. It sounds very awkward. Not used in UK or US.

3) What did happen to you? Sounds awkward, though it looks grammatically correct. I could be wrong on the grammatical correctness.

4) What did it happen to y

I would say the only correct one is 'What happened to you?' or 'Did anything happen to you?'. You can't have two subjects when you use 'what' because 'what' is the subject. However, if you get rid of the particle 'what' then you can have a subject. i.e. Did anything happen to you. Something did happen to me, did the same happen to you?. Miriam help

1. What happened to you?
2. What did happen to you?

The difference between [1] and [2] is the inclusion of the auxiliary verb "do". This is added to secure emphasis, and is called the intensive form. Example:

A: What happened to your face? Did you get into a fight?
B: No.
A: Then what did happen?

Here's an example in the present simple:

I don

Thank you for your help but (always it is a "but") you say (and I agree with you) that "What happened to you?" is common and accepted, so does it mean this sentence is grammatically correct too? Doesn't it seem to you that anyway "What did happen to you?" have to be the only grammatically correct form to ask, regardless it sounds awkward? Maybe it is an accepted slang?
Do you know what's hap

Eladio,

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Yes, grammatically correct too.

Here is the definition of happen: http://www.yourdictionary.com/ahd/h/h0054300.html

2. To take place.

So we could write this

Thank you for all your replies!
Now I feel I found the grammatical rule for this case: "What" and "Who" can be used as subjects in sentences like: "What happened to you?"; "Who phoned me?" and there's no need of using the auxiliary verb "do", which do happens if I say: "When did it happen?" because "When" can not be used as subject (or Why, Where, etc). Is this "rule" correct?

Eladio,

What about "What's happened to you?"

Your rule is correct. It's called "Questioning the subject".

If you want to look at it scientifically, try this:

The question form comes from the statement form. The same statement can generate several questions:

"I went to town to buy a shirt."

1) I went to town for this reason.

1a) I went to town WHY.

1b) Move the question word to