What did/do you call your parents?

Plain old "Mum and Dad".

Sometimes Mother and Father to wind them up. Could never call them by their first names, it would just seem too weird.

Mum and Dad

Just the standard Mum and Dad.

I'faith, nuncle. I would use to call them Dame and Sire.

It didn't last long as I drove them nuts, what with all the "Prithee" that usually tagged along. He whipped all the "marry, nuncle, sirrah, i'faith and prithee" outta me with my own jester's belt, the one with all the bells. This was when I had a part in the schools play, a variation of King Lear.

must be a hell of a lot of brits here since a surprising amount call mom "mum."

I'm on my phone so no idea where people's locations are

When I was talking to them: "Uh".

When I was talking about them: "The olds".

Mom is mom
Dad is "fat man" - this is a nickname he got when I was just starting high school. Not really even sure how it started. I called him that once at church after everyone was filling out and I got a couple people give me weird looks. A couple had "horrified" looks on their face. One of the older ladies asked me about it later and I explained it was a nickname and that calling "dad" across the room would have had 200 people looking at me.

We also do the Marco/Polo thing in the store, so we all look like complete idiots, its just the kind of family I grew up in.

I had a great grandmother who was "grandma odie" because we could not pronounce "zoe"