Margaret

Margaret is the mother of Jake, Finn, and Jermaine. She first appears in one of Finn's flashbacks in the episode "Memories of Boom Boom Mountain." She and 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 vs. Me-Mow," it is revealed that she had a special lullaby for her children. Finn kept her music box in his backpack. It is assumed that he kept it as a memento of her.

She appeared in "Memory of a Memory" while Finn and Marceline were in Finn's memories. She appeared in a photo holding one of her children wrapped in a blanket.

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.

Appearance
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 American 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, arrows and a crossbow.

Quotes
"Give it here, Joshua. This baby just needs some love and kisses to be happy."

"Perform CPR! They might be dead!"

"There, there, baby. You're going to be a fighter. Just like your mother."

Major appearances

 * "Joshua and Margaret Investigations"

Minor appearances

 * "Memories of Boom Boom Mountain" (flashback;debut)
 * "Jake the Dad" (archive footage & flashback)

Mentioned or pictured

 * "Rainy Day Daydream"
 * "Conquest of Cuteness"
 * "Memory of a Memory" (picture)
 * "Jake vs. Me-Mow"
 * "Beautopia"
 * "Hug Wolf"
 * "Jake Suit"

Trivia

 * Margaret is confirmed to be deceased.
 * Unlike Jake, she cannot stretch or expand because she does not have her son's magical abilities.
 * 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."
 * Margaret has grandchildren named T.V., Kim Kil Whan, Viola, Jake Jr., and Charlie, who are born in the episode "Jake the Dad."
 * This would also make Bronwyn, Kim Kil Whan's daughter, her great-grandchild.
 * On the closed captioning on "Memories of Boom Boom Mountain," it says that Margaret is "Female Jake."