The episode begins with the Ice King performing his version of Marceline's Fry Song to Gunter. He then decides to ask Marceline to help him write a song to impress princesses. He rips some pages from his scrapbook so he can use them as inspiration for lyrics and then flies to Marceline's house. Finn and Jake notice him and think that he is up to no good.
Ice King arrives at Marceline's house and asks her for help writing a song. She refuses, and he flies into the house. He tries to let her hear what he has so far for the song, but when he tries to setup his instruments he gets tangled up in the cord. Finn and Jake arrive and try to subdue him, but Marceline tells them that they are writing a song together. They perform a song about Princess Bubblegum and the other various princesses of Ooo, and how the Ice King is sad and alone. He has a breakdown and begins shooting ice bolts at the ceiling, when Marceline tackles him, and tells him to stop acting crazy. He goes into the kitchen, and sits on the fridge. Marceline goes into the kitchen and sings about how the Ice King is crazy, and how she is too for liking him. Ice King asks for a hug, which Marceline gives him. He mistakes it for a beginning of a romantic relationship and tries to kiss her. She explains she only likes him as a friend and asks if he really doesn't remember his past or who he is, calling him by his name, Simon.
The Ice King takes out his pages from his scrapbook while proclaiming that he is a lyricist. Marceline looks at a few of the documents and shows him a newspaper clipping with a photo of himself before he was the Ice King, showing him what he was before the Mushroom War, most notably holding The Enchiridion. Marceline then finds a photo of herself in the pile, which she says he took. The Ice King has no memory of this. Marceline then looks at the back of the photo of herself and finds a message from Simon directed at Marceline, apologizing for his deteriorating mind. Ice King then tells her to sing the message as lyrics, as he plays the drums. Marceline sings the message on the back of the photo, hoping the Ice King will regain his memories. Marceline becomes frustrated that he does not remember anything, and shows him something that he wrote. He sings the message, and gives a look of remembrance, but he is not sure. As they sing, Finn and Jake look inside the house with binoculars, not knowing what's going on.
A flashback reveals a ruined city in the aftermath of the Mushroom War, and a young Marceline standing alone in the wreckage crying. A not-yet-fully transformed Simon runs to her to wipe her tears away and goes to a toy store to give her a stuffed animal that appears to be Hambo, which cheers her up.
- In the Ice King's past room in the bottom left in a box, there is a picture of a meteorite heading for Earth.
- Marceline is the third person to call Ice King "Simon" with the others being Finn and Ricardio.
- The effect of the Mushroom War can be seen in the last part of the episode.
- When the Ice King lifts his tunic he is shown to be fat instead of skinny as seen in prior episodes. According to Cole Sanchez he has just been eating more.
- The instrument the Ice King plays in this episode is called an Omnichord.
- When Ice King was holding the picture while he was singing, it disappeared from his hand.
- When Marceline was singing Nuts it zooms to a ceiling view, and the window that looks into the living room is gone.
- Marceline is wearing a No Smoking T-shirt.
- Ice King mentions prog (progressive) rock, a genre of music that became popular in the early 70's. The popularity decreased but gained a cult following. Innovative prog rock bands include Pink Floyd, Yes, Genesis, King Crimson, Rush, and Emerson, Lake & Palmer. The music was characterized by abrupt changes of tempo, key and time signature, complex rhythms and long songs.
- In the first shot of the "The Past" Room in the upper right corner there is a Highway 101 sign. Highway 101 runs through the Pacific Coast of the United States.
- Ice King sings a variation of the Fry Song in this episode; he was revealed to know of the song in "Holly Jolly Secrets Part II."
- During the flash back to the Great Mushroom War, it's seen that Ice King was the one who gave Marceline her stuffed bear, Hambo, who was earlier seen in "Memory of a Memory."
- There is a newspaper clipping with the Ice King (then known as Simon Petrikov) discovering the Enchiridion in an article from the "Andersonsonian Standard" about Petrikov and the book.
- Betty is seen in the car while Simon is holding the book.
- Under the picture in the article, you can roughly see that Simon delivered the book to the Museum of History. After the Mushroom War, it's likely the book was taken by someone.
- The crown that Simon Petrikov found, and relied upon for survival as revealed by the videos in "Holly Jolly Secrets Part II" is mentioned again in the notes that Marceline and Ice King use in the song as driving Simon crazy but keeping him alive. Marceline is also confused as to why Ice King does not remember her or his notes, meaning that she does not fully understand the power of the crown, nor does Ice King (anymore), as his memory is only able to remember some things about the past, and not comprehend what actually happened.
- During one of the songs that the Ice King was singing, the mention of Princess Bubblegum made Marceline feel uncomfortable, just like in the episode "What Was Missing".
- The book Mind Games by Jay T. Dawgzone from "Reign of Gunters" appears again, advising Ice King that "Chicks dig bros with tortured pasts."
- The Ice King first exclaims that he has a tortured past (referring to his transformation and the Mushroom War) hinting that he remembers very vague, general details about his past, before questioning his own memory and dropping the subject.
- In one scene, Ice King's ruined bass drum from "The Chamber of Frozen Blades" can be seen.
- A sign that appears outside of the diner in "Memory of a Memory" makes an appearance in the Ice King's "The Past" room.
- In "Memory of a Memory," Marceline states to Hambo that it is her only friend; when Simon's transformation into the Ice King is complete, she knows that she is not friends with him anymore, or she may have thought that Simon abandoned her, considering the fact that he left her after having another "episode" for fear of what the crown might make him do.
- Marceline receives a new and brightly colored Hambo from Simon Petrikov at the end of the flashback in this episode, but in the flashback from "Memory of a Memory", Hambo is grayish, raggedy, and missing pieces. Also, Simon Petrikov is not present in that memory, as he may have gone completely crazy by then and left Marceline, giving some clues as to how long it took for the magic of the Crown to turn Simon Petrikov into the Ice King.
- The original title for this episode was "Help."
- Apparently Ice King always eventually finds Marceline no matter how many times she moves which may explain her many homes.
- This is the first time Marceline and Ice King are seen interacting in the series.
- It appears that Simon Petrikov cared for Marceline as a child.
- It is revealed that Hambo was given to Marceline by the Ice King (as Simon Petrikov).
- We also see Hambo's original coloring (red) before he became weathered with age.
- Ice King wrote "Remember You" knowing Marceline would some day read it and understand why he does not remember her, that it was the crown that made him crazy, but kept him alive.
- Although the Ice King is normally quite oblivious to the tragedy of his own madness, it is implied that during fleeting moments of lucidity that he is aware of who he once was and feels the gravity of his past. For instance near the start of this episode the Ice King is seen rummaging through his boxes of keepsakes and as he comes across a scrap book filled with poignant reminders of who he once was he absent-mindedly describes it as "wet with tears" indicating that he must have been recently crying over it even though he no longer appears to remember doing so.
- This episode's title card depicts the Ice King looking into the mirror at a sad reflection of himself with the vestiges of who he once was peaking out from behind the cracked glasses he wore as Simon Petrikov. Given the illustration, it is likely "I Remember You" isn't just referring to Marceline remembering her childhood with the Ice King, but rather the Ice King remembering glimpses of the soft spoken antiquarian he once was before the power of the crown consumed him. This also explains the meaning of the episode's original title of "Help".
- Ice King may be seen as a replacement father figure for Marceline, instead of Hunson, during the time after the War until the point he turned completely crazy from the magic of the crown. He may have been a family friend before the War, though this is mainly speculation based on Marceline's comments.
- In the final scenes of the episode during the song, the world can be seen after the War, in ruins. There are buildings, cars, jeeps, military vehicles, undetonated warheads and many pieces of glass and plaster on the ground. The building on fire and the lack of foliage taking over the barren earth implies that the war was just recently ended before Simon encountered young Marceline. There are also a number of spent shell casings around young Marceline's feet.
- When Ice King was singing "Remember You," he frowned while looking at the paper, but then started smiling again at the chorus. They could mean that he remembered for a bit, or was confused by what the writing was saying, but if he did remember for a while he must have ignored it because he smiled after singing that part he went on to a cheerfully drumming.