What's happened? = What has happened? = Present Perfect Tense What happened? = Simple Past Sometimes they are used interchangeably, but you use the present perfect if something happened recently and is important for the present situation. A: Please call the ambulance? B: Why? What's happened? A: In the movie Titanic, two young people fall in love while traveling on a ship. B: Then what happened? / What happened next?

Tale of Revenge, In British English the rule is fairly strict: if an action in the past has present consequences you use the Present Perfect. In American English the Past Simple is often used. (The Present Pefect is also used and is also correct). The connection to the present is understood either by context or by a key word (just, already, etc.) Examples British.....................................American I've already eaten............I already ate. I've just arrived.................I just arrived. Has he eaten yet?..........Did he eat yet? Or take the case of the question "What happened?" If something has just happened (and it is obvious to everyone that it only recently happened) in America, the past simple form can be used. Example: Imagine there is an accident scene and you walk up and ask "What happened?". Everyone understands that you are referring by context to the present situation and not something that happened twenty years ago. So in that type of situation Americans feel free to use the Simple Past. In formal American English the Present Perfect is preferred but in popular writing, movie scripts, advertising, and just plain everday speech Americans often use the Past Simple when referring to the recent past. Of course, both forms are correct and unless it is your mission to teach Americans to speak British English, you should be prepared to understand the differences.

what happened is in the past tense what's happened is what has happened: present continous they are used for the same thing e.g. when a kid comes home from school with his clothes dirty: Mum: what happened? or what has happened? Boy: i fell off my bike. some people prefer to use present continous for things that happened recently and still have an effect : past tense is ok too as this thing already happened