Joshua is a dog who is the father of brothers Jake, Finn, and Jermaine. He and his wife Margaret adopted Finn as a baby. He speaks in a 1940s Mid-Atlantic accent. Joshua's personality is demonstrated as an old-fashioned manly dog who is willing to push his sons to fight, particularly when they need to.
Joshua first appeared with his wife in one of Finn's flashbacks in the episode "Memories of Boom Boom Mountain." They find Finn after he has soiled himself causing him to be stuck to a leaf. Finn claims to have cried for a whole day before anyone helped him. They are the first to stop and help the seemingly abandoned baby Finn. They take him to what is presumably their house and raise him as their own.
Joshua returns in "Crystals Have Power," where his ghost appears from beyond the grave encouraging Jake to fight back against the Crystal Guardians of the Crystal Dimension after Jake takes a vow of non-violence. Jake became upset when he remembered Joshua telling him that "Jake would hurt everyone." Jake also sees his brother Jermaine in his flashback. It should be noted that Joshua was trying to tell Jake that "Jake would hurt everyone... who is evil. Let me finish next time."
During "Crystals Have Power," Jake says "stupid ghost dad" when talking to himself out of frustration after Joshua says "Come on, punch them Jake. Punch everybody. Why not? Come on, why not!" Also, when Joshua brings Jermaine to see Jake, Jake asks him if he is dead, implying that Joshua is already dead (Jermaine was not dead, he and Jake were just dreaming at the same time).
In "Dad's Dungeon," Joshua makes Finn and Jake (through pre-recorded Holo-message player tapes) explore a dungeon he made. The dungeon is filled with traps and monsters to toughen up Finn. Joshua puts Jake's family sword at the end of it as incentive to go through its trials.
Joshua is confirmed to be deceased. He, as well as his wife Margaret had passed away prior to the events of Adventure Time. The cause of death is unknown. In "Dad's Dungeon," the hologram video shows Joshua being attacked by a Giant Monster, this may have happened after Jake beat Jermaine.
Although Joshua does not possess stretching abilities like his son Jake, he is still a really tough, skilled dog who had created a reputation for himself in Ooo prior to his death. He prides his physical toughness and the ability to fight and stand up to any evil that gets in his way. Joshua also has some skills in magic, knowing spells such as one to banish the Demon whose blood he used to make the Demon Sword. He may have some swordsmanship abilities, but they have not been demonstrated as of this time. After his death, he still possesses some abilities, such as the ability to talk to Jake in his dreams if needed. While deceased, it seems he can summon "spirit sparkles," though it is unknown if all Ooo spirits can do this.
- "Memories of Boom Boom Mountain"
- "Crystals Have Power"
- "Memory of a Memory" (photograph)
- "Beautopia" (mentioned)
- "Dad's Dungeon"
- "King Worm"
- Unlike Jake, he cannot change his size.
- When Susan draws a picture of a Lub Glub, Jake says, "That looks like my father."
- Both he and Margaret speak with 1940s Manhattan accents.
- Joshua's appearance above on the profile is like Jake, only he is wearing a hat. But he is a bit darker than Jake's color.
- Joshua appeared in "King Worm," where he is seen knitting with green yarn.