Simple Past Tense:
* "What happened to your car?"
* "I happened to see her at the grocery store."
* "The accident happened right in front of my house."
Past Perfect Tense:
* "I was surprised to hear that she had happened to be in town."
* "It had happened so quickly that no one could react."
* "By the time the police arrived, everything had happened."
With a prepositional phrase:
* "It happened to me last week."
* "The fire happened at night."
* "The meeting happened in the conference room."
As part of a question:
* "What happened?"
* "How did that happen?"
* "When did it happen?"
In a conditional sentence:
* "If it had happened to me, I would have been furious."
* "I would have left if it had happened again."
Remember that "happened" is often used to describe something unexpected or unplanned. It can also be used to simply describe an event that took place in the past.