The Journal is a special hour-long episode in the Hey Arnold! TV Series. It is the final episode made for television.
Arnold finds his father's journal, which tells the story of how his parents met, how they got Abner, his birth, why they went on their "last" trip... and one last surprise.
Part 1Arnold is on a ship traveling with his parents, Miles and Stella, and all three of them are happy to be on this adventure together. When he spots a ship, Miles sees that it belongs to pirates and he and Stella go off to deal with them, leaving Arnold at the helm. They start firing cannonballs at the ship, eventually destroying it. He doesn't see them or his parents anywhere and yells for them to come back. He then wakes up in his bedroom and finds that it was all a dream.
He is feeling sad because today is October 5th, the anniversary of the day that his parents left him and never returned. He is too sad to do anything with his friends and turns down an offer to go to Dinoland with them, wanting to be alone today. While Helga and the others mock him for not wanting to go, Gerald learns why he is feeling sad and gives him some sympathy. Helga actually stays behind and hides, overhearing the whole thing and feeling remorseful for mocking him. Later in the day, he packs up all of his parents' things to put them in the attic. Grandpa tries to talk him out of it, but he says it's time to move on and decides he doesn't want to hear any more stories about them.
As he puts away the packed box, he stumbles upon a journal, then realizes it belongs to his father. He is excited to have found it, and Grandpa determines Miles must have written in it during the time he was in San Lorenzo, which is located in Central America. Arnold, Grandpa, and Grandma gather in the living room and start reading the journal, and whenever Grandpa reads a story, it takes us into the past with Arnold's parents.
Miles comes to San Lorenzo as part of an anthropology research party, which includes his college friend Eduardo, and meets a botanist/physician named Stella, who is there studying the local plant life in hopes of finding cures for jungle illnesses. As time passes, they spend a lot of time together (mainly because he keeps injuring himself and getting treated by her) and fall in love.
One day, after hiking up the cliffs and falling down the ravine into a river, they are saved from falling down the waterfall. While they don't get to see their savior, they realize that it was one of the elusive Green Eyed People, the original inhabitants of San Lorenzo. They decide to thank them by their own good deed, and when they learn from Eduardo that a local river pirate and treasure hunter named La Sombra stole a relic called La Corazón from the Green-Eyes, they decide to recover it as a way of paying them back . They succeed in getting it back and return it to them by placing it on one of their ancient shrines.
On their wedding day, Miles and Stella are given a piglet from the Green-Eyes as a gift, who grows up to be Abner. After the wedding, there is an implication of them about to conceive their child, but just before anything else is shown, Grandpa rips out the page and lies to Arnold about it.
While on their honeymoon in Rio de Janeiro, Miles and Stella save a group of people from a broken-down cable car. Soon afterwards, they are asked to come back to San Lorenzo by Eduardo after they learn that the Green-Eyes have been struck by a disease. Because Stella is a doctor, along with the fact that they only trust them, she and Miles are the only ones who can help.
Part 2Stella determines that the Green-Eyes have been affected by a sleeping sickness, and they work together to gather the ingredients for a serum to treat them. After they succeed in making it, they drop it off at stone monument marked by their architecture (similar to a shrine where they returned La Corazón).
It is afterwards that Stella discovers that she is pregnant and months later, when she is in labor, Eduardo and Miles carry her to town on a makeshift cart, but they get cut off in the jungle when a volcano starts erupting. They discover a temple of the Green-Eyes and find a bed ready for her. Right when she gives birth, the eruption stops and a baby is heard crying among the silence. Eduardo says that "he has silenced all of nature." Miles and Stella are blessed with a son named Arnold, and call him "a miracle baby." Arnold wonders whether his parents ever found out the cause of the miracle, to which Grandpa finds no explanation.
Back in their village, they are having trouble raising a rumbustious baby Arnold, but they love him nonetheless. One night, after he crawls out of the hut and nearly has an encounter with a snake, they realize that they can no longer stay in San Lorenzo and go back to Miles' hometown of Hillwood.
Miles's parents, Phil and Gertie, are pleased that they're home and love their new grandson. A year later, they all celebrate his first birthday together, and Miles and Stella take him to the park where they buy him his tiny blue hat. When they aren't looking, he escapes from his stroller and climbs up the slide. He falls down and lands in mud but is unharmed. They are happy that he is safe, then they vow that they will never let him out of their sight again. On another day (not mentioned when), Eduardo pays an unexpected visit to tell them that the sleeping sickness has broken out again in San Lorenzo and many Green-Eyes have already perished. Although it hurts them because they don't want to leave Arnold, they decide to go, as they are grateful for the Green-Eyes helping them so many times before. They believe that their trip will be fast and they will be back very soon.
In the present, Arnold, Grandpa, and Grandma are all heartbroken after having read the last story, for they know that what was meant to happen never did. But Arnold is happy that they found the journal because he had learned so much more about his parents and understands why they left. He just wishes that he knew what happened to them.
After his grandparents go to bed, Arnold goes outside on the stoop to look at the journal again. When he comes to the last page, he finds the one final surprise: a map, which he realizes is the route his parents took on their last trip to San Lorenzo. He goes inside and yells to his grandparents about his discovery.
When Nickelodeon ordered the final three half-hours of Season 5 in 2001 (after deciding to release the TV movie Arnold Saves the Neighborhood theatrically as Hey Arnold! The Movie), they also requested Craig Bartlett to make a double-length "prequel" episode that would tie the television series to the second movie, which was in pre-production at the time. According to interviews, Bartlett initially did not like this idea.
- This episode exists on two versions: a two-part version and a full 47-minute version. TV Networks that air Hey Arnold! in half-hour slots show this episode in two parts; however, other networks that air the series in hour slots (or run marathons) show the full episode.
- In the two-part version of this episode, part two begins with Phil giving a recap of part one.
- Arnold's birthday is commonly agreed to be on October 7th, the date the first episode "Downtown as Fruits" aired in 1996. Miles and Stella left on October 5th, two days before his birthday. This suggests that they disappeared two days before Arnold's second birthday.
- This episode slightly retcons how Arnold got his blue hat. In "Arnold's Hat", it was given to him indoors, but this episode shows Arnold's parents giving him the hat outdoors.
- Storyboards from this episode show a couple of deleted scenes. One of Eduardo eating spicy soup, and another of an exchange between Miles and Eduardo that's extremely similar to the exchanges between Arnold and Gerald.
- The Republic of San Lorenzo is a reference to the Kurt Vonnegut novel Cat's Cradle.
- Volcán Turrialba, the volcano that erupts on Miles and Stella's way to the hospital, actually is a real-life volcano in Costa Rica.
- Stella wears a tanktop similar to what Lara Croft wears in the video game Tomb Raider.
- Grandpa doesn't know the meaning of Stella's name. It is the Latin and Italian word for star. It is the feminine version of the male Greek name Stelios, a name used to honor St. Stylianos, an orthodox saint.
- Miles telling Stella not to look at the Corazon is a reference to the movie Raiders of the Lost Ark, when Indiana Jones says not to look at the Ark of the Covenant.
- Miles "hates spiders" much the way Indiana Jones "hates snakes".
- In the scene where Miles snd Stella save a group of people on a cable car, Miles screams "Stella" in a reference to A Streetcar Named Desire.
- Grandma references the 1971 Allman Brothers song "Ramblin' Man" when she says that she thought Arnold "was born in the back seat of a Greyhound bus rollin' down Highway 41."
- When Stella gives Arnold his name, she says "It was my father's name", which implies that his other grandfather had died before he was born.
- Abner was almost eaten again in the episode "The Pig War".
- Arnold now keeps the picture of his parents in a frame. In the episode "Parents Day", it was in a paper one.
- The ride Stinky mentions at the beginning of the episode was seen in the episode "Roller Coaster".
- In some scenes, Baby Arnold wears a light blue shirt and diaper, which is the same attire as Tommy Pickles from Rugrats.
- The music for the credits is a remake of Parents Day End Credits.
- The "sleeping sickness" to which the Green-Eyed People fall ill may be a reference to the real-life American trypanomyasis (chagas disease) which is caused by parasitic infection by the protozoan species Trypanosoma cruzi and transmitted by the tsetse fly and kissing bug.
- The voice of the younger Harold is the only one of the babies who had their voice actor reprise them (the audio itself was reused from Helga on the Couch).
- Pookie confuses Miles and Stella's wedding with the Wedding of Charles, Prince of Wales, and Lady Diana Spencer.
- The "lucky numbers" on Grandpa's fortune cookie are 13, 13, and 666. 13 is infamous for being an unlucky number, and 666 is the Number of the Beast.
- This is one of the only episodes to use production music (and not music composed by Jim Lang). One of Dick DeBenedictis' (a composer best known for his action/horror production music) production tracks "The Shock" was used when the cable car breaks down and another track called "Nervous Tension 3" was played when the volcano started erupting.
- Innuendo: When Phil was reading the page that was written and told about after the wedding - the scene where Miles and Stella were simply smiling at each other - he immediately closed book swiftly after reading "oh there was the..." and made excuses for Arnold to briefly leave the room so Phil could get rid of that page. It is appparent that this scene explained that Miles and Stella were about to get intimate, and Phil did not want to read this sort of adult material to Arnold as he was too young to know these sort of things yet.
- Baby Arnold's toy bus has his last name "Shortman" on the front of the toy.
- Despite this being the last episode of the series on production and chronological order, it was aired in the U.S. before four other episodes of Season 5, creating a continuity error in the American broadcast.
- This episode first aired on June 27, 2002 on YTV, and it was later aired in Latin America on September 2002. Both of these countries aired this as the true final episode of the series.
- When Helga takes out her locket while behind the car, Arnold is missing from his stoop.
- Elk and peafowl can be heard in the San Lorenzo jungle, however both animals are not native to Central America.