Finn and Jake's parents hunt an unearthly menace in the woods.
The episode opens up in the treehouse where Finn, Jake and BMO are celebrating Jake's birthday. As Finn and BMO chant "Birthday," Jake gobbles his birthday cake. Finn mentions to Jake how he's a year older but still looks good, Jake replies saying that it's thanks to their "Mom and Dad" passing down good genes. Finn begins to remember his foster parents, Joshua and Margaret, prompting him and BMO to ask Jake to tell a story about their parents, a "Birthday story." Jake then proceeds to tell his story.
The scene changes into a flashback when Margaret was still pregnant with Jermaine. Margaret is seen fiddling with her crossbow when Joshua interrupts her with dinner, two steaks. As they were eating the steaks, Margaret told Joshua to check for new cases. Joshua refused at first, as he was concerned about Margaret managing in her child-bearing state, however she managed to convince him she could handle it. As Joshua looks through the cases, he finds a case described as 'Woman's pies going missing'. They left their house and drove their car to Tree Trunk's House to investigate. Upon their arrival, Tree Trunks complains about a monster that has been stealing her pies, when suddenly they encounter Wyatt, climbing in through the window.
Wyatt then revealed that he was the one who ate the pies, and planted false footprints wearing a pair of tennis rackets on his feet. Joshua and Margaret then assumed the case closed, and prepared to leave, but Tree Trunks informed them that there was still a real monster nearby, due to her getting rubbed on her elbow. They decided to investigate the scene, Joshua reluctant, but doubting the credibility of the claim, therefore assuming it would be alright for Margaret to come along. Upon reaching the location, they found actual footprints of the alleged monster.
Following these footprints, they were led into the forest surrounding Tree Trunk's house. Joshua was becoming increasingly convinced that an actual monster existed, became more worried about Margaret and moved they discontinue the case. However, Margaret ran deeper into the forest, forcing Joshua to follow. They followed the footprints into the brush, when suddenly a strange blue cat lept out of a bush in front of them. The blue cat turned out to be a shape shifter, its true form later seen as a Shape-shifter. The creature bit Joshua on his head, causing Margaret to pull out a pin from her hat and shank the creature in its side, wounding it. Hurt, it ran back off into the forest, dripping 'blood' on its way back to it's lair.
Back in their house, Joshua is seen with a bandage on his head, covering the wound where the Shape-shifter's venom quickly spread after entering his body. Joshua suggested that Margaret end his misery and kill him with his sword. However Margaret wouldn't hear it, and quickly tried to find an antidote for the venom in the Book of Poisons. The book stated that she needed to obtain more venom from the creature to develop the antidote. She got geared up with ammo, weapons, and defense, and donned a new hat. After leaving a walkie-talkie next to Joshua, to allow them to stay in contact, she set off in search of the creature. The scene changes to Margaret parking her car back in the forest, following the trail the creature left behind when she suddenly found herself in the creature's lair. When she called Joshua on her walkie-talkie to check on him, we see Joshua at home with bulging veins. He accidentally steps on the walkie-talkie, crushing it, and we see a blue lump growing on his head as he moans.
Back to Margaret looking for the creature, she shone the flashlight around, trying to locate the creature. She shot some arrows with her crossbow but missed, as the creature suddenly shapeshifted, dodging away and next to her. It shapeshifted into many animals before it finally approached Margaret. She reached for her crossbow and fired upon a stack of boxes, causing them to fall on the creature. It then shapeshifted into a baby-like-creature to lure Margaret closer, but when she was close enough, she sucker-punched the shape-shifter, and drained its venom into a test tube. Margaret leaves the lair, apologizing while walking backwards to the exit, but as soon as she was gone the creature suddenly shape-shifted, creating a portal, then shapeshifted into a blue ball and entered the portal.
Back in the house, she found the interior of her home in a wreck. As she was moments away from having the baby, she was in a bit of pain. Margaret entered the kitchen looking for Joshua and found him outside. She jumps out the window to see Joshua with strained veins and the huge lump on top of his head. Margaret, still having troubles with her baby, yelped in pain and noticed that Joshua's blue lump was fit to burst. After another yelp, they heard a loud splat noise and they shone the flashlight in the direction the sound came from. Joshua had essentially given birth to a puppy, Jake. Puppy Jake then sang and danced before falling back to sleep. Joshua and Margaret were both in shock, when suddenly Margaret's belly began moving a lot and she screamed.
The scene jumps to a forest with Joshua pushing a stroller with Jermaine and Jake asleep in it. When Joshua mentions the scar Jake left on his head, Margaret pulls out a fedora and places it atop Joshua's head. They discuss Jake's origins, and whether or not he could be a harmful creature. They decide to accept Jake as their son, and agree to never reveal to Jake how he was born.
The scene changes back into the present in the treehouse, whereupon Jake finishes 'And so they never told me.' Finn is confused on what Jake wasn't told, and questions it, but Jake replies saying " I don't know! They never told me!"
- Jermaine (flashback)
- Snail (flashback)
- Tree Trunks (flashback)
- Wyatt (flashback)
- Kee-Oth (pictured)
- Fire Demon (flashback/mentioned)
- Jumping Citizens (flashback)
- This episode was announced during the 2014 San Diego Comic Con along with a sneak preview of the episode.
- It is revealed that Jake is not biologically related to Margaret.
- This episode also explains how Jake got his stretching powers from being half shape-shifting creature, proving that Jake was wrong about getting his powers from rolling around in the mud and that he is actually a hybrid between a dog and the shape-shifting creature.
- It also explains why Joshua always wears a hat.
- Tree Trunks uses the regional pronunciation "Leftenant" when referring to Lieutenant Candy Corn.
- The demon in the picture Margaret shot with a crossbow was Kee-Oth.
- This episode's title is the longest in the series.
- The book Margaret was reading about the antidote is named 'Book of Poisons' and a long text on both pages can be seen. Among this texts:
- It states 'according to the WHO'. In modern day, the WHO is the short form of the World Health Organization, the specialized agency of the United Nations dealing with public health.
- It also lists "Cleopatra, one character in an Arthur Conan Doyle story," which refer to an actual historic person and an actual author in modern day.
- Furthermore, Cleopatra committed suicide by having a poisonous Egyptian cobra bite her. The character refers to The Adventure of the Speckled Band, where Dr. Roylott is killed by adder venom.
- The spine of the book sported a skull and crossbones, which symbolizes poison, among other things.
- Joshua and Margaret are a homage to Nick and Nora Charles from The Thin Man book and film series of the 1930's and 1940's.
- The scene where Warren Ampersand bites Joshua is very similar to the first attack in the Parasyte manga.
- While Jake being born of his father Joshua is similar to the birth of the creature from the 1979 movie Alien, him immediately singing and dancing after birth is exactly like the parody situation in the 1987 comedy Spaceballs. In both the original and the parody, John Hurt portrayed the "father" of the creature.
- Jake being born from Joshua's head and already having abilities to talk, sing and even dance may be similar to the myth of the birth of the Greek goddess Athena, who was born adult and fully realized from Zeus' head.
- In Margaret's weapon room, a Poké Ball from the Pokémon series can be seen on the right side.
- Margaret refers to Jermaine, while she is still pregnant with him, as 'ankle biter'. Ankle biter is an Australian slang term for a small child.
- This episode reveals the origin of Jake and his stretching powers, which had been hinted at an unknown even to Jake; prior to this episode he had thought in "The Witch's Garden" that he had gained them from rolling in a magic mud puddle as a puppy; however it is closer to Princess Bubblegum's theory from "Wizards Only, Fools," where she states his powers are mutation when he tries to explain that he is magical. It likewise reveals the connection he has to his half-brother Jermaine, who is technically his brother but "younger" due to being born mere moments after Jake as first noted in "Crystals Have Power."
- When Jake is first born he rolls in a puddle of fluid from the boil in Joshua's head- this may be his vague memory of getting his powers from rolling in a mud puddle.
- At the time this episode is taking place when Tree Trunks is married to Wyatt who was first seen in "Apple Wedding." He is currently one of her three ex-husbands.
- The background of Flame Princess in "Earth & Water" was also mentioned, though she was called "fire goblin" again, similar to in "Hot to the Touch."
- Joshua says "small fire goblin" as when Flame Princess was little.
- The Demon Blood Sword first introduced in "Dad's Dungeon" can be seen on the left side of Margaret's weapon room.
- If Joshua did not start wearing his hat until after giving birth to Jake, then this would contradict the order of events since he was wearing his hat when he tricked Kee-Oth into creating the Demon Blood Sword. It is possible that Joshua owned the hat beforehand, or that the sword is made from another demon's blood.
- In "Beautopia," when Susan tries to explain what a "lub glub" is, she draws a picture that vaguely resembles the creature when it was creating its portal. Jake responded by saying that it looked like his father and later saying the same thing about his mother. This could be a reference or just a coincidence.
- After firing an arrow at the picture of Kee-Oth, Margaret pumps her fist and says "Yus!" Finn also does this in a few episodes, such as "Ocarina."
- When Margaret prepares to find the Shape-shifter, she has 3 ninja stars, and when she comes back with the venom, she now has two. But when she finds Joshua in the alley, she has three again.
- Margaret does not appear pregnant in the title card.