He is voiced by Jack Jones.
The frogs true origin is unknown; however, he shares a striking resemblance to the frogs on the Frog Boat. He is also seen singing the opening theme,"Into the Unknown", at the beginning of the show. In "Into the Unknown" Greg asks Wirt to go frog hunting with him. They do not end up going frog hunting, but Greg found it soon after he and Wirt crossed the garden wall. He states that they found it on their frog hunt, even though they did not officially go. Greg has trouble deciding on the frog's name and often changes it.
Journey in the Unknown
Greg had given the frog the name "Kitty" as a possible name for the frog. After receiving temporary refuge from the The Woodsman, he points them in the direction to the nearest town and since Greg's frog is his opportunity, he suggests him to give him a proper name, Greg then thinks of proper names he could give the frog and comes up with giving him the name "Wirt Jr." after his big brother. He goes through other names in the series, such as "Doctor", "Jason Funderberker", and more.
After meeting Beatrice, who claims a nice women named Adelaide of the Pasture can send the boys back to where their home and take a frog boat ride to get there, during their trip the Frog police come to arrest the brothers, but run and disguise themselves as one of the band players performing on the boat ride. To make sure their cover isn't blown they try to join the band in music and accidentally knock out the bassoon player, but with no bassoon player the frogs start to panic. Beatrice convinces Wirt to play the bassoon instead and does so beautifully. As the music starts Greg's frog begins to sing Over the Garden Wall during the boat ride. After they reach their destination Beatrice convinces the brothers to wait until tomorrow to meet Adelaide. After seeing Beatrice fly off on her own, Wirt and Greg follow her, leaving the frog behind. After discovering Adelaide was actually going to imprison both Greg and Wirt, they escape and kill her in the end. Wirt now felt betrayed by Beatrice and decided not to trust anyone else, Greg's frog arrives to the brothers and continues the journey.
After losing Beatrice, Wirt believes he can lead by himself and leads them both to a supposedly abandoned house where they find a girl named Lorna and her guardian Auntie Whispers. The brothers believe Auntie Whispers is a cannibal and plan to help Lorna escape from her auntie who can control her with the use of a magic bell. After Greg's frog wanders off into Auntie Whispers room he eats the bell and the brothers hide in a closet with Lorna. They now discover Lorna was the cannibal all along and flee from her. Wirt uses the bell which is inside the frog to get rid of the evil spirit from Lorna forever and now they can live a happy life.
Greg sacrifices himself to save Wirt from the beast, Wirt tries to look for him and accidentally falls into a lake and almost drowns. Thankfully Beatrice's family had rescued Wirt and had taken both him and the frog to the family's tree home. After waking up from a dream on how he and his brother first entered the unknown by falling in a huge pond. Wirt takes the frog and goes to find Greg.
After finding Greg who has almost turned into an Edelwood tree, Greg asks Wirt to give back a rock he had stolen from their neighbor, but encourages him to return it himself saying they had to get the frog which he names after his rival, Jason Funderberker home and Greg sees Jason Funderberker as the perfect name for him.
After returning home, Wirt brings both Greg and Jason out of the pond and the brothers as well as Jason are taken to the hospital. Greg relays to Wirt's friends about their adventure in the Unknown and tells them his frog Jason Funderburker, which the human Jason mistakes for himself.
- Wirt (and later, Wirt Jr.)
- George Washington
- Mr. President
- Benjamin Franklin
- Doctor Cucumber
- Greg Jr.
- Jason Funderburker
- Jonathan Livingston Applesauce (In the comic series)
- In the intro and ending of Over the Garden Wall, the frog is heard narrating and playing a piano.
- On the official tumblr page, it is stated that Jason the human spells his surname as "Funderberker", while Greg's Frog spells it as Funderburker, to avoid confusion.
- In the Unknown, Jason knows English as he narrates and sings in the show.
- During the finale of Over the Garden Wall, it shows the adventures of the Unknown may have actually happened, as shown when Greg was shaking the frog. There was a faint glow, which could have been from the bell he swallowed in The Ringing of the Bell
- In the comic series of Over the Garden Wall, Greg's Frog was called: Jonathan Livingston Applesauce, Private Applesauce, and Johnny.