Not really sure if it qualifies as a 'dad joke', but I laughed my arse off. He was telling me about a joke he played on my mum when they were younger, before I was born.
We're from Australia, and there's a lot of places out woopwoop that are just empty. Him and mum were driving in the middle of bumfuck nowheresville, and they came up to a train crossing. Only thing is, because of where it was, there weren't any boom gates; it was just the track cutting through the middle of the road. On each side of the road was really high grass, so he actually had to poke the car out a bit so it was on the tracks to be able to see on either side. So he pulls the car out (in Australia, the driver is on the right side of the car instead of the left), and he looks to his right. No train coming. He looks to his left, and mum also looks left. Dad sticks his hand out the window, screams NO!!! and slams his hand on the side of the door really hard. It scared the shit out of mum so much that she actually started crying. He told me this and we both posses ourselves laughing for about 10 minutes.
At the dining room table, younger sister is talking about her intro to Spanish class and I passively mention "I was never really good at rolling my r's."
Right after I say this, my stepdad begins sliding in a circle in his chair. When I finally say "What are you doing!?" he responds:
"I'm rolling my arse."
Walking through the supermarket and talking with the missus about something or other, when she laid me an opportunity on a plate.
Her - "I'm just not gonna tell her. No need to deal with the hassle - the prevention is better than the cure."
Me - "Really? I've never heard them before. Any songs you'd recommend?"
It took a second for her to figure out what I meant, and I ended up with a kick up the arse for it, but it was worth it regardless.