Harold is a bright green frog with a yellow underbelly and brown orange eyes.
Harold has no speaking parts but is seen in the background of many scenes.
- While Harold has never been shown as an integral character in any canonical instances of Cow of the Wild's story, he is present for many events that take place over a considerable span of time. His appearances in the show include:
- Episode 1 - "Child's Play", where he is pursued by a young Luna who has wandered away from her mother, Blue.
- Episode 3 - "The Fence", croaking idly nearby as Alari greets Milly through the fence and teaches her to howl.
- Episode 4 - "Those Lost", sitting beside Bone as he mourns the disappearance of Alari.
- Episode 7 - "Omega", watching as Luna is kicked from the den and starts itching herself.
- Episode 10 - "Leaving Home", present as Luna answers Milly's howl, much to Lupis' frustration.
- Episode 13 - "New Places", startling Sammie as she searches the forest for Milly.
- Episode 15 - "Good and Bad Intentions", witnessing Midnight's emotional abuse at the hands of Fang.
- Episode 16 - "Coming Togethers", standing behind Luna as she has her ear talked off by Rocky. Moments later, in the wide shot of wolves visiting the Pack of Night for Fang's meeting, he is also seen being badgered by a visiting wolf.
- Episode 17 - "Things Best Left Forgotten", being stalked by a young Lupis prior to Rune murdering his whole family.
- Episode 21 - "Romance is Boring", awaiting Fang in his den alongside Midnight.
- "Not just a frog - The frog. He is a warrior of truth and justice - an immortal monument to all things glorious, and good, and free. An ageless agent of the divine. He goes by many names. The one he choses to disclose to we puny mortals is Harold."
- —Tribble about Harold