Margaret is the adoptive mother of Jake and Finn, and the biological mother of Jermaine. She first appears in one of Finn's flashbacks in the episode "Memories of Boom Boom Mountain." She and her husband Joshua found Finn after he had soiled himself, causing him to get stuck to a leaf, after he cried for an entire day, all alone in the forest. They were the first and only people to stop and help baby Finn, as all other passersby simply ignored him. She is nearly identical to Jake. They took him to what is presumably their house and raised him as their own. Margaret appears to be caring and loving.
According to Finn in "Conquest of Cuteness," Margaret always knew "the right thing to say" whenever he or Jake were in a crisis. Strangely, a Two Headed Cutie tried to exploit their love for her during their invasion, pretending to be her ghost mocking them in an attempt to find their weaknesses.
In "Jake the Dad," it is revealed she recorded a holo-message with instructions on how to raise puppies. However, she was far too over protective and considered everything as a possible threat to child safety because her own manual did the same.
In "Joshua and Margaret Investigations," the story flashes back to when Margaret worked with Joshua solving cases and having adventures while pregnant with their child. She is shown to be an extremely strong dog like her husband, expertly wielding a crossbow while heavily pregnant and seeking out a mysterious monster in the woods despite Joshua's efforts to keep her home and safe, risking her life to get an antidote when Joshua is poisoned. It is ultimately revealed that the child she was pregnant with was Jermaine, not Jake, who is not her biological child but rather a hybrid created from a shapeshifting alien creature who infected Joshua. This is likely why she reacted with shock to Jake's exhibiting his stretchy powers to battle a cobra in a flashback in "Jake the Dad."
Margaret, as well as her husband Joshua, had passed away prior to the events of Adventure Time. The cause of death is unknown.
Margaret looks similar to Jake, but has eyelashes and wears a peach-colored hat with pink laces, yellow ribbons and blue and fuchsia-colored designs and blue and pink earrings. She speaks in a 1940s Mid-Atlantic accent.
In "Joshua and Margaret Investigations," she wears a red hat with a pink flower on top and a scarf of the same design. Later, she wore the peach-colored hat as mentioned above, with an ammo belt with several test tubes, shurikens and a flashlight on. She also carries a quiver of arrows on her back and a crossbow.
In "Joshua and Margaret Investigations," Margaret was shown to be skilled at using the crossbow. She was also shown to be very capable of enduring her labor pains as she showed herself to be able to walk throughout the whole process until the birth of Jermaine.
Give it here, Joshua. This baby just needs some love and kisses to be happy.
Perform CPR! They might be dead!
—"Jake the Dad"
There, there, baby. You're going to be a fighter. Just like your mother.
You're about as fine as a canary in a cat mine!
- "Joshua and Margaret Investigations" (flashback)
- "Memories of Boom Boom Mountain" (debut, flashback)
- "Jake the Dad" (archive footage & flashback)
- "The Comet" (comet projection)
- "Whipple The Happy Dragon" (hallucination)
- "Orb" (dream)
- "The First Investigation" (video and time slip)
Mentioned or pictured
- "Rainy Day Daydream"
- "Conquest of Cuteness"
- "Memory of a Memory" (picture)
- "Jake vs. Me-Mow"
- "Hug Wolf"
- "Jake Suit"
- "Everything's Jake"
- "Take Her Back"
- "Jake the Starchild"
- In "Rainy Day Daydream," Jake accidentally imagined his mother naked when his imagination machine was set to overdrive. However, Margaret "naked" (without her hat and earrings) would be an ordinary dog like Jake, but to him that could be a traumatic thing. However, he could have imagined her without her fur as well.
- In "Beautopia," Jake sees the largest and most grotesque of the Lub Glubs and says with awe, "That reminds me of my mother," a probable reference to the creatures' resemblance to inkblots used in Rorschach psychological tests.
- It is unknown how old Finn was when she died, since he has many fond memories of her.
- In Finn's flashback in "Memories of Boom Boom Mountain," Margaret first referred to Finn as "it."
- The storyboard for "Memories of Boom Boom Mountain" reveals that her original name was "Martha."
- On the closed captioning on "Memories of Boom Boom Mountain," it says that Margaret is "Female Jake."