Throughout the series, Golf Ball and Tennis Ball maintain a friendship. There is also a possible romantic relationship going on. Golf Ball said in Take the Plunge: Part 2 that she only liked Tennis Ball in a platonic way (like siblings), after Coiny claimed that TB and GB had a crush on each other. In Lofty, they were fighting about whether the cloud looked like a golf ball or a tennis ball. However, this is the kind of thing siblings do. They still maintain their friendship in BFDIA, IDFB and BFB. Tennis Ball also follows Golf Ball's instructions. Many fans call this relationship TenGolf Ball.
Like Pen and Pencil, they have a lot in common too. They're both sports balls, don't have any arms, and are very intelligent.
Episodes showing a friendship
- BFDIA Intro: Tennis Ball is sitting right next to Golf Ball. However, it could just be a coincidence.
- Insectophobe's Nightmare: Tennis Ball said to Rocky that he and Golf Ball are a duo. And both of them was seen tying their legs together.
- Half a Loaf is Better Than None: Tennis Ball is seen cheering for Golf Ball in the Loaf Contest.
- Zeeky Boogy Doog: When everybody is recovering everybody with the HPRC, Tennis Ball chose to recover Golf Ball.
- Every time Golf Ball manages her team, Tennis Ball is her assistant.
- At some point, they are just talking to close to each other.
- IDFB Intro: Golf Ball is once again close to Tennis Ball.
- Welcome Back: Tennis Ball and Golf Ball go together to the science museum of Yoyle City.
- Getting Teardrop to Talk: Tennis Ball helps Golf Ball find Leafy and Golf Ball lets Tennis Ball help her manage A Better Name Than That.
- Lick Your Way To Freedom: Tennis Ball tried to defend Golf Ball when 8-Ball replaced Golf Ball as team leader.
Episodes suggesting a conflict
- Lofty: In the beginning of the episode, Tennis Ball and Golf Ball are arguing about the ball-shaped cloud.
- Today's Very Special Episode: Tennis Ball was also obeying 8-ball instead of Golf Ball, which doesn't connect due to him trying to defend 8-ball to not replace him. He even tried to prevent her from drawing their Four make-over.