Which tense and what is the verb conjugation?
I just want to clarify the following phrases if they are correct:
"¿Qué os _______ (pasar)?"
Would the conjugate of "pasar" be "pasó" if the question was referring to an event which occurred in the past? Also, why is it not "pasasteis" as "os" is present in the phrase.
"Ayer nos ______ (occurir) una cosa increíble"
Would the conjugate be "ocurío" because its is referring to "una cosa increíble"?
Os and Nos are the Indirect Object pronouns, indicating "to whom" the action is occuring. The verb is conjugated based on the subject. In the first case: "What happened to you?", the (unspoken) event (the "What") is the subject, so it is third person singular - pasó. In the second, "an incredible thing" is the subject, as you indicated, so again, third person singular occurió".
¿qué os pasastéis? if you are using the reflexive form of the verb and you are saying something like: What happened to you(plural)? but if you just want to say. What happened? you would just say: ¿Qué pasó? the other one is: Ayer ocurrió una cosa increible. Can't see any need for nos here.