The series only shoots for three days per week. Louis C.K. has custody of his children for the rest of the week and refuses to shoot on those days. On those days, he edits the episodes while his children are at school. According to C.K., the crew dislikes the schedule but has to accept it.
In the opening credits, when Louie is in the pizzeria, a passerby can be seen extending his middle finger at the camera. This was not planned. According to C.K., he saw this as good sign that the show would get picked up and he decided to leave the finger in the opening.
Louis C.K. has said that continuity is not hugely important to his series, with each episode having its own "end goal". Louie's immediate family has been a major example of this. In Season 1, two different versions of his mother appeared (one a miserable, selfish old woman, and the other a kind and likable middle-aged woman) and he had a loser brother named Robert; in Season 2, his mom doesn't appear, and Robert no longer exists, having been replaced by two sisters (one a likable, tough, pregnant woman, the other a mentally ill mother of a sullen teenager) and Season 3's finale introduced another sister portrayed by Amy Poehler. Different actresses have occasionally been used to play his daughters; however, they're almost always played by series regulars Hadley Delaney and Ursula Parker, with just a few exceptions.
The pizza place that Louie goes to in the opening credits is Ben's Pizzeria in Greenwich Village, Manhattan in New York City. In real life, Louis C.K. frequents the pizzeria.
When writing the fourth season, Louis C.K. found himself writing so much of a story line that he ended up having more like a movie screenplay, about 180 pages. He decided to shoot it anyway and make into parts, resulting in the six-part "Elevator" episodes.