Transcript for Louis CK, the Everyman's Comic

Louis ck, the edgy, profane, everyman's comic. Now something of an every man's guru with his no hold barred approach making him an expert on topics as varied as sex, parenting even getting old. Because with perfect comic timing the ugly truth can be a beautiful thing. And he goes face to face with ABC's Diane sawyer. ? Louis Louis Louis ? Reporter: Funny philosopher king of life as we live it where everything is a little bit good and a little bit hopeless. How you doing? Okay. Good. On his show and offscreen he shares custody of two daughters. All right. Reporter: And documents the reality of girls and the unglamorous guy. I'm the guy that women see and they go, eh. I'm like, I know, let me just talk to you for a minute. I would look to make one of those it gets better ads for just dumpy young guys. We can use a little help. A little encouragement. Just somebody on TV, listen man, I know it is tough right now. You are vaguely heavy with no face. You have zero value on the sexual marketplace. You feel invisible to the girls in school because you are. But it gets better. Also featured his favorite pizza joint in greenwich village. On the show he writes, directs and edits. After a battering start. Do you look in the mirror every day and assess how you look? Oh, god no, I would die, wouldn't make it through. Reporter: Always been that way. Did you have a period where you thought, cool? Looking good? About myself. No. No. Reporter: Never, never in your whole life? That I thought I looked cool? No, no, I never liked the way I looked. In high school I had thick hair. I hated it. I was pale and skinny and weird looking. Reporter: His biography full of surprises his mother American, his father a Mexican economist. Don't his daughters resent he didn't teach Spanish to them. They can resent whatever they want. You look ahead at your children's future resentment. Reporter: Life changed when they divorced and heap a and his sisters were with mom in Boston. A hard worker, my mom. Reporter: Your dad, see him, talk to him? Not so much. Some times a parent/kid relationship turns into a friendship later in life. Some times it doesn't. That's the way it works out. Isn't it good? It's really good. Now here he is a television dad and a kind of parenting hero. Well that's not fair. I don't even know what that means. Why does she get one and not me? Because she is a separate person from you. You are never going to get the same things as other people. Never going to be equal. Not going to happen ever in your life. Learn that now. Reporter: On Twitter, attacking core curriculum in public schools for taking the joy out of math. These are my little feelings. I don't believe that they should matter to anybody else. But 3 million Twitter followers, so, you know. I grow on people, women, when you get, some time goes by, you get past the bald head and like sweat a lot and lumpy. I have run out of things to say. Can you just say, tell me now, if it is working, are you going to? I don't dig guys, I'm a lesbian. I think sex is a fascinating subject. And a hilarious subject. It is awkward. And it is high stakes. And it makes you feel great or makes you feel terrible. It is a huge array of experience. Sex. So it is well worth talking about. It is what most people are thinking abut most of the time. So why not talk about it. Back on TV, talking to parents who want the truth. It is "Saturday night live." I went to my daughter's play the other day. I don't know if you have kids. There is no more joyful feeling in the human experience than when a child's play is over. It's just -- nothing feels that good. That's who I am. I am a real man. Reporter: You get a feeling that alongside the truth teller is a kind of poet of hope and haplessness, laughter, and lonliness. Sometimes I just feel like I, I don't have any friends. And why do you think that is? I don't know. Do you think it's because you're fat? Louis, like a friend, familiar, and consoling. We have this feeling of your benevolence? I don't know, oh, man. Is that wrong? I don't know. That you kind of want everybody to be whole and their dreams not to decompose and -- Well dreams decomposing is not a bad thing for some body to go through. I think if everybody's dream comes true, that's a bad scene. That's not a good idea. I don't wish for people to have all their dreams come true. I wish them to be okay with the fact that they won't. You know what I mean I you can go out into the world -- not letting it stop you -- when things don't go your way, then you are unstoppable. You know what I mean? There is nothing that can beat you as long as when some body goes, no you can't. You go, where else can I go. No, all right. No, thanks anyway. Thanks anyway. What will get you through life I think. Reporter: Especially since sometimes when it is 4:00 A.M. And the dark night of the soul. Daddy. Reporter: You never know who will come by to say, let's go get some pancakes. ? ? ? had a real bad night ? For "Nightline," I'm Diane sawyer in New York.

This transcript has been automatically generated and may not be 100% accurate.