I never knew anyone who calls their father pop, except Lamot Sanford 
That would be a good hijack to this thread, TV characters that call their father “pop”
From the Mary Tyler Moore Show
My husband’s kids and stepkids call him “Pop”. It’s the only time I’ve heard it in real life.
I’ve called my father Dad all my life, and he called his father Pop.
Lately I’ve noticed a growing tendency to call my father Pop. It’s just a little alarming insofar as I don’t want to turn into my dad. I do like it, though; it’s a lot more jovial and friendly IMO, whereas Dad is a little more kiddish.
My dad’s father abandoned their family when the children were all very young (the eldest of 5 being in 1st grade). Those kids refer to their father as “The Old Man.” I don’t believe I have ever heard them call him by name. The Old Man died a couple of years ago and we didn’t even know until a friend-of-a-friend sent a copy of the obit to my dad.
I call my dad “Old Man” playfully, as in, “Watch it Old Man” if he is irritating me or teasing me about something.
In Ham radio - OM in code is how you refer to a male ham op, typically the senior guy. OM stands for Old Man.
Since all of us in my family are Hams (Amateur Radio Operators), as soon as my brother and I learned that it was correct and proper to call the Old Man an Old Man - that is what we started calling him when our Federal Licenses arrived in the mail.
“Dad” has seemed much the most common in my experience. “Pop” sometimes is a term of convenience when somebody else is already Dad. “Old man” is generally reserved for “so’s your old man!”
I don’t think I’ve ever heard anyone in real life using those terms.
But when my father became a grandfather, he didn’t want to be called Grandpa because that’s what you call old people. He taught my niece to call him Papa. She ended up calling him Pop Pop, which he didn’t like. He was Grandpa after that. The maternal grandfather was Grandpa Dick.
I (33yo WM) call my father “pop”. Always have. I think it started with Dr Seuss’ “Hop on Pop.”
My kids call me “Pops” and have for as long I can remember. My grandkids all call me Pop-Pop. I take this as a term of endearment.
The kids call my wife “Moom”. They used to call her “mom” but one of them mistyped it in an email; it must have been 25 years ago, since he was still in college, and she used it in her reply and it sort of caught on with all three. To the grandchildren, she is “Nana”.
I normally refer to him as “Dad”. But occasionally at family gatherings, I will call him “Old Man”.
Ha ha, now that I think about it, I was a cigarette smoking high school drop out* when I started to call my father “Old Man”.
*I since quit smoking and re-enrolled in school, so I have no idea what that makes me now.
In rural Oxfordshire where I grew up, not only was “my old man” the standard for “father”, we also had:
My old boy = brother
My old gal = sister
My old dear = mother
If you want to aim for authenticity, “my” is pronounced “moy”. “Old” is pronounced “ow”. “Boy” is pronounced “buoy”. “Gal” is pronounced “gaw”.
My old boy calls my old man “pops” but it’s ironic.
I don’t hear and haven’t used “Pop” much. My father often referred to his father as “the old man,” though, so I’m accustomed to hearing that. I associate it with an older generation. Like DigitalC, I sometimes call my father el viejo. He lived in South America and Mexico for many years, and we both speak Spanish.
I call my dad Pop (sometimes Popsicle if I’m being funny). I’m under 30 and it’s not regional, I just do. I don’t really call him “Old Man” but sometimes when he calls I answer by saying “What’s up, old man?”
My sisters and I all went through periods of calling our father Pop, before ending up with Dad. I think it might have been a 1950’s thing.
Oddly enough, I recall my old-enough-to-be-a-grandfather father calling his father “puppa” – obviously something left over from the old country.
My dad called his father Pop, and so did his sisters. My dad started doing it very consciously when he started school–sixish? He’d grown up speaking Polish at home, where “dad” is tata. But kids made fun of that–what’s the most all-American you can get–“Pop” it is. My dad refers to his (late) father this way still. “Pop and I…” never “my dad and I.”
I’m 63 and have never used the term “Old Man” for my father. It has always been Dad.
Also, I’ve never used the term “Old Lady,” to refer to my wife.
I started calling my old man Pop around the time I grew out of calling him Daddy at age 7 or so.
He was Pop until he died when I was 35.
My brother sometimes calls my father “Pop”. He’s experimented with a number of different names for my parents – the most annoying was when he called them “Ma” and “Pa”. I think of my father as Dad or Papa, but when I actually speak to him, it inevitably comes out as Daddy. This can be embarassing when I’m calling him in a public place.
My oldest brother calls my dad “pop”, but it’s mainly because my dad isn’t his real dad. He raised him from the time he was roughly 3 years old, but my brother still knew his real father so he always referred his biological father as “dad” and my dad as “pop”. Still does.