I could swear that in my younger days people used “Que pasa?” as an alternative for “What’s happening?” “How you doin’?” or just plain “Hey!”
But now it’s all about “Que paso?”, often with the last syllable drawn out for emphasis. When I’ve asked Spanish-speaking acquaintances about it, they look at me as if I’ve just suggested putting ketchup on a taco.
So, did it change? When? Why? Somebody tell me what’s happening!
¿Que pasa? is Spanish for “What’s happening?" (Spanish uses the simple present where we tend to use the present progressive; the literal word-for-word translation would be “What happens?”, a highly improbable though syntactically sound English construction.)
¿Que pasó?, on the other hand, is preterite, and basically means “What happened?”, or, in casual usage, “What’s been going on?” (which would technically call for the imperfect or present perfect, or even present perfect progressive, but the simple preterite works in casual use).
In today’s Mexican speech, I would hear “que pasó” more often than “que pasa,” although I have the same memory as the OP. “Que pasó” (instead of “que pasaba” as Polycarp mentions) is more common. For truly present occasions, I’d hear “que honda” instead of “que pasa” these days.
Thus the humor sketch where a “language expert” tries to define “onda” by showing pictures to a teenager
1st picture, a swimming pool : teenager : “Esta pileta es honda!” (this pool is deep) (the H in honda is silent in spanish)
2nd picture, a police patrol car: teenager : “uhhhh, mala onda!” (uhh, bad vibes!, uncool)
3rd picture, a lot of motorcycles of diferent brands: teenager: “Cual es la Honda?” (which one is the Honda? / Whats the vibe here)
4th picture, the opening scenes from “Reservoir Dogs”: Teenager: “esto es una onda Tarantino” (This has a Tarantino vibe/mood).
Where is she from? My girlfriend is from Guatemala and she says “qué pasó” for “what’s up?” even though it doesn’t make sense to me, and actually sort of bugs me because I think of that in my head as “what happened?” and I always want to respond “nothing happened”.