Dads are funny. You can't argue otherwise. Dads have an entire joke genre that is named after them. The Dad Joke is often cringeworthy, but I'd argue that it's the best type of humor in the world. It can be applied during any situation. Dad Jokes are battle ready. They are always in a dad's holster, ready to fire. I can really appreciate that, even if some of them (most of them) are groaners.
The thing that makes a dad joke so good is that the person doesn't realize that they are setting themselves up for a joke. They are just living their lives then BLAM. Dad Joke. This dad's joke is an incredible burn. It's a bit of a self burn, but that's OK. If the son were to come back with a line about looking like his dad, I'm sure the dad has a dad joke block he could use.