The guardians are robots that resemble gumball machines, due to their spherical glass heads and the colorful gumballs inside them. They have pink bodies and wear an ice cream cone hat. They are tall enough to easily step over the walls of the Candy Kingdom.
The Gumball Guardians were designed and built by Princess Bubblegum to protect the citizens of the Candy Kingdom. They became operational during the time while the kingdom was still under construction. In their early days, the guardians referred to Princess Bubblegum as their "mother" and primarily focused on protecting her rather than everyone in the Candy Kingdom. In addition, they were nuisances for the residents of the kingdom, especially during the night, as they would often loudly question them about their safety.
The Gumball Guardians can utilize a wide range of offensive abilities for defending the Candy Kingdom. Their primary method of attack is through the use of lasers that can be fired from both their eyes and their mouth. In addition, the Gumball Guardians can breathe fire and use runic lasers that are capable of causing large explosions. Due to their immense size, the guardians are very strong, making them proficient hand-to-hand combatants. In "Sky Witch," the Gumball Guardians were given the capability to release sleeping gas into the air.
The guardians also have the ability to detect evil presences within the boundaries of the Candy Kingdom. This allows the Gumball Guardians to pinpoint their targets with great precision as shown in "Little Dude," where they recognize Finn's hat as a threat despite its small size. They also are able to put a stop to Peppermint Butler's demonic rituals on the top of the Candy Castle in "The Suitor." In addition, the Gumball Guardians can see through the disguises of evil entities as, in "The Lich," they reveal that Billy was actually the Lich wearing the hero's skin. The guardians' ability seems to have some limitations, as they were slow to confront Little Dude, Peppermint Butler, and the Lich.
The Gumball Guardians have the ability to manipulate time and space, as revealed in "Slumber Party Panic." They automatically freeze time if a person breaks the Royal Promise and seize them to put them through a trial by fire. The guardians can also reverse time if the individual who has broken the Royal Promise receives a pardon by Princess Bubblegum and correctly answers a given math problem.
The guardians have a few minor abilities which include the projection of holographic images with their eyes and the production of both simple and complex math problems and their answers.
Finn the human! You have broken a royal promise, for which the penalty is trial by fire.
Oh wait, wait. I thought of a better one.
Evil presence detected! Must defend!
Lich alert! Lich alert!
MUST DEFEND Candy Kingd... wraghhhhh
Peanut Butler, eh, Peppermint Butler, cease these dark magic activity.
- "Slumber Party Panic"
- "Mortal Recoil"
- "Reign of Gunters"
- "The Lich"
- "Little Dude"
- "The Suitor"
- "Sky Witch"
- "The Vault"
- "Love Games" (fantasy)
- "James II"
- "Hot Diggity Doom"
- "The Invitation"
- "Come Along With Me"
- "Trouble in Lumpy Space"
- "The Enchiridion!
- "Ricardio the Heart Guy"
- "The Duke
- "What Have You Done?"
- "To Cut a Woman's Hair"
- "Susan Strong"
- "Go With Me"
- "Too Young"
- "Fionna and Cake" (Ice King's fan fic)
- "From Bad to Worse"
- "Five Short Graybles"
- "Bad Little Boy" (Ice King's fan fic)
- "Five More Short Graybles"
- "Candy Streets"
- "Earth & Water"
- "Something Big" (deactivated)
- "Bonnie and Neddy"
- "The Empress Eyes" (far background)
- "Take Her Back"
- "The Dark Cloud"
- "Angel Face"
- "Blank-Eyed Girl"
- "Jelly Beans Have Power"
- "Diamonds and Lemons"
- There is a model of a Gumball Guardian in Princess Bubblegum's lab. It is seen after the real Guardians leave her and Finn.
- In "Slumber Party Panic," Princess Bubblegum seems to be unaware that a math problem can be chosen as an alternative penalty for breaking the Royal Promise, despite her being the creator of the guardians.
- In "Ricardio the Heart Guy," when Finn decides to spy on Ricardio, one of the Royal Guardians appears to be missing his cone hat.
- In "Ricardio The Heart Guy," there are two smaller Royal Guardians in the throne room where Ricardio holds Princess Bubblegum hostage. They are seen wearing royal cloaks and blowing horns.
- A Royal Guardian's head is seen in Jaybird's lair in the episode "Apple Thief."
- In "Mortal Recoil," one of the Guardians has his glass bowl head broken without consequence, but in "Reign of Gunters," when Gunter threatens to do the same, the Gumball Guardian reacts as if such an act would be fatal.
- They are set off by "evil presence," which they can detect. However, neither Ice King nor Marceline triggers this reaction, suggesting that despite those characters' respective origins as a wielder of dangerous magic and a demon/vampire, they are not of evil alignment.
- Marceline was even able to push a Guardian out of the way, enter Princess Bubblegum's tower, and close the curtain without raising any objection from the Guardian, suggesting it has no problem with her or this behavior.
- They are bosses in Adventure Time: Explore the Dungeon Because I DON’T KNOW!
- They are similar to Benson from Regular Show in that they are both based off of gumball machines.
- In "Mortal Recoil," the way the Guardian speaks resembles the dialect used by the Daleks, from the sci-fi TV series Doctor Who.