Everyone has vastly different relationships with their fathers, but as we grow up and move away from our parents, if you're lucky enough to have one of your best friends be your dad, it's a pretty great dynamic a lot of people don't always understand.
1. You call him about everything.
Whether it's car issues to gloating about you just ran a mile without twisting your ankle, he answers eager to know what's going on. He may go to bed at 9pm every night but that doesn't stop you from calling him at 1am because you can't remember the year your first dog died and the thought is keeping you awake, and he still answers every time. And if he doesn't answer, you don't hesitate to call 4 more times before even leaving a voicemail, and he usually answers on the third time anyways (probably because he's worried something is actually wrong.)
2. You guys laugh hard at things no one else seems to think is as funny.
You almost have to apologize to everyone else that doesn't find it as funny, because you'll keep egging each other on about the same joke until something new comes up. Inheriting his sense of humor is probably something you'll thank him for forever.
3. He supports you through things he doesn't agree with.
To the neon colored jeans phase you went through in middle school to wanting to be a pro tennis player to the boy you dated in high school, he supported it so you could learn to express yourself and be who you wanted to be. He has no issue telling you when he thinks your making a bad decision and what he thinks would be better, and it's totally his place to say it as your dad, but ultimately he supports the choices you make, and reminds you he's proud of you.
4. You can have fun with anything.
Grocery shopping, hiking, going out for lunch, going to the gym together, trying new things, no matter what it is, it's always a blast and you almost always learn more about each other while doing it.
5. You're both each other's "venting buddies."
He knows what makes you tick, and so when you complain that your best friend did just that he's ready to back you up. On the same note he complains to you about little things too, because you guys think so similarly it's never negative.
6. You can't imagine life without him around.
No matter how busy your life gets, you can't imagine what it's going to be like when he's no longer one phone call away. He's your number one fan, your strongest line of defense, your dorky equal, and your best friend.