Doug finishing his song for his ex-girlfriend Margy after an argument between the two of them about how he never finishes anything. He later gets the song put on an album called "I Told You I Wrote The Damn Thing".
In "The Whine Country" Doug screws Carrie out of a vacation in Paris by wanting to go on a trip around the country in an RV. She retalitates by inviting her father along, resulting in this exchange, which always makes me laugh out loud:
Doug: (pounding on hand for emphasis) I don't want your father in my Roadbird.
Carrie: Why not? We got that great table bed, right?
Doug: Yes we do. But I don't want to eat breakfast on a table that recently held your father's ass. That's ass breakfast!!
"You know, I just remembered what I wanted for dinner. A nice hot bowl of shut-it stew!"
Any shutty variations. In no order: Shutty, Shut it uppie, Shutty town, Shut up sickle, shut it stew, shut it up industries, and "once again, this area, shutty shutty!"
From "Animal Attraction" ("Mother of ass!"), we also have "Wild Cards" ("I hate my own ass!") and Doug singing "Brandy (You're a Fine Girl)" from the episode "G'Night Stalker".
In "Lost Vegas", Doug allows Carrie to go to a wellness spa in hopes of earning "credit" so he can go to Vegas with his pals. Carrie is suspicious, but Doug claims to be a "new and improved Doug." After the Vegas trip falls through, he tries to get something else out of the deal, resulting in this exchange:
Carrie: Oh my God, there's no new and improved Doug, there's just the same old lying, selfish Doug.
Doug: I like to refer to it as "Doug Classic."
Also, "Trash Talking" featuring Jon Favreau as Doug's "enemy" from junior high. Some of the highlights:
"[Doug laughs as Sean leaves, then shuts the door] I hate that son of a bitch."
"Have fun playing with your pal Sean McGay. Man, I wish I'd thought of that back in junior high."
"Don't play? What are you, on pot?"
"Too much cheese? In-sanity!"
"Did you lick it?"
Carrie: Didn't you once tell me you ate that feed they have at petting zoos?"
Doug: My sister told me if I did I could grow a mustache."
In the first season, Doug finds out that all the women of Carrie's family stay slim easily up to a certain point, then suddenly start gaining a lot. He catches himself looking at her stomach and worrying about the fact that she can no longer fit in her wedding dress. So he tells her that, to be romantic, he's going to carry her up to bed. But as soon as he lifts her in bridal position across both arms, he jiggles her to see if he can see or feel any extra fat.