During the visit to the Stark family home in Chapter 1, Jack sees Willie's childhood bedroom and immediately has a rich vision of Willie's childhood. This goes on at some length, beginning as follows:
I looked over at the bed, and the crockery wasn't there. It was the only prop missing. That and a kid with a pudgy face and freckles on his face and sandy hair falling down on his forehead, bending down at the table by a coal-oil lamp—it must have been a coil-oil lamp then—and a pencil in his hand, tooth marks on the pencil where he'd been gnawing on it, and the fire in the trash-burner getting low [...]
Jack looks around the room, and sees that the "crockery"—a chamber pot, which Willie calls a "thunder-mug"—wasn't there. (Jack is not above scatological humor.) Then, though, he realizes that something else is missing from this child's bedroom: a child. Jack then eagerly imagines young Willie studying on a cold night. This method of storytelling is common throughout the book. Almost involuntarily, Jack's imagination takes him on non-sequitur digressions into the past. This is the primary method by which Jack presents background information. Here, though, as often in the novel, Jack presents these events as a real flashback, but they seem to be the product of his imagination of Willie.
This imagined flashback continues to tell a longer tale of Willie's late-night studying: the wind whips frigidly across the panes while the young Willie sleeps on his hard, cold bed, dreaming about his future. Jack imagines Willie's mental state: "He wouldn't have any name for what was big inside him. Maybe there isn't any name." Even in this vision of the past, Jack is obsessed with Willie's ambition and seeks to understand what drives Willie so strongly.
Then, Jack flashes back to the present: "That was all there was missing from the room, the kid and the thunder-mug. Otherwise it was perfect." This flashback, the product of Jack's imagination, is a reminder to the reader that this is Jack's story and not necessarily any verifiable truth. Still, though, it animates the story and helps to build Willie's character. But note how, as often in the book, Jack's admiration of Willie causes him to contradict his own philosophy. Jack thinks that the highest goal in life is truth and knowledge and often uses this fact in his arguments about God. But visiting Willie's childhood bedroom, Jack is happy to imagine Willie's past without regard to the truth, which shows how fascinated Jack is with the character of the Boss, going back to childhood.
Late in Chapter 1, Sugar-Boy drives Jack through Burden's Landing. Jack is overwhelmed with nostalgia and imagines himself as a boy:
At night you pass through a little town where you once lived, and you expect to see yourself wearing knee pants, standing all alone on the street corner under the hanging bulbs [...]. Why, this is Jack Burden. Don't you remember little Jack Burden? He used to go out in his boat in the afternoon on the bay to fish, and come home to eat his supper and kiss his beautiful mother good night and go to bed at nine-thirty.
Jack frames this flashback in an unusual way. He says that "you expect" to see your young self in your hometown, projecting his nostalgic impulse onto the reader. From there, Jack describes that young self, although it is not clear how truthfully he does so. He ventriloquizes an unnamed character from Burden's Landing, speaking about himself, and his childhood innocence and playfulness.
This flashback gives the reader information about Jack's emotional state, even as it seems as if he is describing a rosy vision of his past. Jack immediately imagines his childhood self when reaching Burden's Landing and feels the need to create a character who still remembers his innocent, idyllic childhood. It seems clear that Jack feels he has experienced a loss of innocence since that time. Jack shows how reverent he is toward the influential families in Burden's Landing (including the Irwins), as he is still thinking about whether they thought he was an admirable little boy. This passage also shows Jack's particular affection for his mother and his assumption of her moral purity; thus this passage serves to strengthen the eventual reveal of Jack's mother's infidelity.
Visiting the man he thinks to be his father in Chapter 5, Jack observes the Scholarly Attorney attending to George, the former circus performer he has taken in. The Scholarly Attorney dotes on George, in this moment leaning over him tenderly, feeding him a piece of chocolate, and cooing at him gently. The Scholarly Attorney, while ignoring the man he believes to be his son, looks at this old, insane stranger and calls himself "Daddy." Jack is, understandably, taken aback by this. Looking at the Scholarly Attorney, Jack's imagination bursts into a flashback:
I was looking there at the old man, [...] who was holding out another morsel of chocolate and who was clucking soft, and whose own face was happy, [...] and as I looked at him I suddenly saw the man in the long white room by the sea, the same man but a different man, and the rain of the squall driving in off the sea in the early dark lashed the windowpanes where the rain ran down to thread and the night-black glass with silver [...]
The Scholarly Attorney seems pleased with his new arrangement. But Jack sees him "in the long white room by the sea." It is unclear whether this is a real flashback to a room by the sea or if Jack is imagining a fictitious past. These sort of debatably real flashbacks are a common narrative device in the novel. But this house certainly seems like it could be in Burden's Landing, which is also on the seashore. In the flashback he imagines "the man" in a more peaceful place; the wind and rain "was a happy sound and safe because the fire danced on the hearth and on the windowpanes."The Scholarly Attorney was "the same man but a different man," clearly identifiable but changed nearly beyond recognition.
So Jack imagines in this flashback that the Scholarly Attorney has experienced a fall from grace, from a peaceful life, seemingly with a more normal domestic dynamic, to the strange situation in which he now finds himself, disheveled in a squalid apartment coddling a mentally ill old man. This type of fall from grace is one of the great themes of the book: Willie, Irwin, and the Scholarly Attorney all have an acute fear of some moral failing that will cause them to lose their exalted position. Jack, in a flash of self-pity after seeing his father neglect him, has a vision of this fall from grace occurring.
Chapter 7 of All the King's Men includes an extended flashback to Jack's first courtship with Anne Stanton, after he learns that she was having an affair with Willie. In his total shock and sadness, Jack sets off on a drive to California and remembers the beginning of his relationship. The flashback begins when he was 21 and Anne was 17. Jack had been friends with Adam since childhood, so he knew Anne, but here he describes seeing her on a fine summer afternoon and immediately falling in love with her:
She was wearing a white linen dress, cut very straight, and the straightness of the cut and the stiffness of the linen did nothing in the world but suggest by a kind of teasing paradox the curves and softnesses sheathed by the cloth. She had her hair in a knot at the nape of her neck, and a white little ribbon around her head, and she was smiling at me with a smile that I had known all my life but which was entirely new, and saying, "Hello, Jack," while I held her strong narrow hand in mine and knew that summer had come.
Jack describes Anne's clothing in great detail, which works as imagery to describe her character. The white dress represents Anne's purity and youth. She is, again, only 17 in this flashback, significantly younger than Jack. Also, throughout the novel, Anne is known for her somewhat naive morality and pure worldview, a relative innocence also represented by the color white. He also describes how her dress covers her figure. Jack's flashback describes Anne in this way because, in the novel's main timeline, Jack feels entirely betrayed by Anne due to her affair with Willie. As he frets about Anne misrepresenting herself in the modern day, so too does he imagine her 17-year-old self hiding things with the cut of her dress. (This jealousy and misogyny is one of Jack's least admirable traits.)
However, through all of this Anne is still described as being uniquely beautiful, and in a testament to the depth of Jack's affection, as if holding her hand is like the beginning of summer. Jack's love for Anne is still apparent despite his anger and sadness over her duplicitousness. In sum, the way that Jack's flashback depicts Anne—beautiful, innocent, but seemingly hiding the truth—shows the reader his complex opinions toward her at this point in the novel.
After Jack learns that Anne has started an affair with Willie, he imagines his and Anne's relationship, some decades before. Near the end of this extended flashback in Chapter 7 is one of the climactic moments of the novel. Alone in Jack's mother's house, Anne lies down naked on Jack's bed in a "gentle curling motion." Anne waits for Jack to join her, expecting to have sex for the first time. But Jack hesitates:
At the instant when she closed her eyes, as I stared at her, my mind took one of the crazy leaps and I saw her floating in the water, that day of the picnic three years before, with her eyes closed and the violent sky above and the white gull flashing high over, and that face and this face and that scene and this scene seemed to fuse, like superimposed photographs, each keeping its identity without denying the other.
Jack is taken aback by Anne's act of total vulnerability and has a powerful and instant flashback. These brief flashbacks happen often in the novel and are a fundamental part of Jack's storytelling. But here, he clarifies that this is a flashback that he actually had in the moment, one of the "crazy leaps" his mind makes. This distinguishes this flashback from others in the novel, where it is unclear if Jack is actually imagining the past or using his imagination.
In the flashback, Jack remembers a picnic that appears at a few points in the novel. In Chapter 3, which contains the most thorough description of the picnic, Jack says that while he didn't fall in love with Anne that day, he will still always remember the picnic as a special moment in their relationship. He has a very rich memory of this picnic, as described in Chapter 3: "The image I got in my head that day was the image of her face lying in the water, very smooth, with the eyes closed, under the dark greenish-purple sky, with the white gull passing over." Three years later, with Anne naked on the bed in front of him, he remembers this picnic again, down to the cloud cover and passing gull. Remembering this event made him feel that "everything was wrong, completely wrong, how I didn't know, didn't try to know, and that this was somehow not what the summer had been driving toward." Jack loves Anne and finds her beautiful, but as her younger self blends together with her current self, like "superimposed photographs," he finds he cannot have sex with her.
This flashback amplifies the tension of this climactic scene of the history of Jack and Anne's relationship and explains why Jack did not consummate the relationship in this moment. It is also an example of Jack's prodigious memory and precise storytelling in action. The entire framing of this scene is worth repeating: Jack, writing after Willie's death in 1939, describes how, in 1936, having found out Anne started an affair with Willie, he had an extended flashback to when he was 21, and within that memory, describes another memory three years before that. All the King's Men is a story that relies on Jack Burden's memory, and this passage describes better than any other its true power.