Tome of the Unknown is from Cartoon Network Studios’ shorts program and won the best animation short film at the Santa Barbara International Film Festival in February 2014. It is written and directed by Patrick McHale, who is also known for working on Cartoon Network's Adventure Time. The pilot episode aired in film festivals such as LA Shorts Fest and Ottawa in September 2013, and at Austin Film Fest in October 2013. On May 19, 2015 the pilot episode released on Cartoon Network.com.
Wirt, his brother Gregory, and Greg's frog travel alongside a bluebird named Beatrice in search of a book known as, "The Tome of the Unknown." The book is described as containing all that has ever been forgotten. When the group of heroes grow tired of walking, Gregory suggests finding a goose to ride. However, Gregory finds a car belonging to a romantic songster made of vegetables. The vegetable man, named John Crops, dreams of traveling to the Big City and finding a gal who will love him and put an end to his loneliness. Therefore, Wirt drives to the city in John Crop's vegetable car in hopes that Gregory, Beatrice, and himself can keep the car if John finds his soulmate in the city. As the gang is traveling in the vegetable car to the city, a horde of crows attacks them which leads the car to veer off of the road into a crop field. While Wirt and Beatrice fix the vegetable car, Greg walks along with John to the city where John meets the Cabbage Gal, who seems to take a liking to him. However, when Wirt knocks down a scarecrow, the crows attack once again, wreaking havoc in the city. Fortunately, Greg scares them away by letting out a loud scream. Wirt is deeply concerned, thinking that his brother could have been hurt, but it turns out that he yelled because he found a large goose that they can ride on, as he suggested to them earlier in the chapter. John Crops then moves out into the country with his new gal while Wirt, Gregory, Beatrice, and Greg's frog continue their journey, on the goose, further into the unknown.
- "Tome of the Unknown" has been adapted into a mini-television series on Cartoon Network titled Over the Garden Wall.
- During the ending scene of The Unknown (episode), Lorna can be seen reading a book titled "Tome of the Unknown".
- A popular song from the early 20th century was sung by John Crops. It is called "Shine On, Harvest Moon".
- Tome of the Unknown has an episode title which is "Harvest Melody". This can be seen in the title card in the beginning.