Banana Joe is an anthropomorphic banana with googly eyes and a mouth made of clay similar to Clayton's. He wears and treats his "peel" like a shirt - he can remove it at will, and has several extras messily stuffed into his clothing drawer. The bottom end of his nude banana body is clefted to resemble his booty.
Being the class clown, Banana Joe is always making jokes or trying to be funny, though his jokes can sometimes be hurtful, like how he teased Gumball to tears in The GI. His jokes can also be annoying or creepy, such as in The Third. At first, Gumball and Darwin enjoyed his comedy act, but as he went on, he got creepier, causing them to leave him.
Banana Joe also has a distaste for girls. This was prevalent in The Pressure, where he established a pals before gals pact with the guys. He even resorted to chopping down the girls' clubhouse, all to prevent Darwin from kissing Masami. However, he may have gotten over this, since he didn't complain in The Party when everyone had to get a date to attend. Furthermore, in The End, he acts as the justice of the peace for Gumball's wedding.
He also appears to be messy. His room is in desperate need of cleaning - his peels are sticking out of his drawer and there's junk scattered across the floor. Also, the stuff in his locker looks as though he just carelessly stuffed them in there.
- The Third: Gumball and Darwin considered making him their third friend, but they found him too annoying and creepy.
- The End: He serves as the parson for Penny and Gumballs' wedding.
- The Pressure: He created a "pals before gals" pact with Tobias, Gumball, and Darwin. Upon hearing that Darwin was to kiss Masami at the treehouse, he grabbed his axe and chopped it down.
- The Mystery: He suggests that Gumball was the one who put Principal Brown in a locker. He also participates in the chase scene.
- The GI: He mocks Gumball repeatedly, causing Gumball to cry.
- The Robot: He randomly yells "I'm a banana!", then runs off screen.
- The Picnic: He can be seen walking with the rest of the class.
- The Goons: He participates in the "dumb" race.
- The Club: He and Tobias are the sole members of The Football Club, who don't actually do anything for the team.
- Whenever Joe does an exaggerated or just large motion, his googly pupils spin around inside the eyes.
- He has a Bananan the Barbarian poster in his room, a reference to Conan the Barbarian.
- His personality and appearance is based on the term "Top Banana".
- His name is similar to "Banana" Joseph Montione and the 1982 film.
- His personality appears to change in almost every episode.
- Banana Joe placed 8th in the Dumb Race.
- He does not like his dad to dance with him as seen in the bannana dance video when he throws his skin on his father.
- In episodes The Dress and The Third he doesn't seem to have a butt like in the "Banana dance" video.
- He is the founder, president and CEO of Banana Joe Studios.