One of Billy's ancestors was a trained rocket pilot and the first monkey in space. Whether by genetic predisposition or not, Billy's ability as a pilot is truly exceptional, and he's the first monkey to enter the F-ZERO Grand Prix. He was raised in a special lab where he was educated in human literacy and communication skills. The lab concurrently developed an F-ZERO racer suitable for a monkey, and bestowed upon him the honor of piloting it in the Grand Prix.
Although he is the first monkey to enter the F-Zero entry, this is actually a misnomer. He is actually of a simian race indigenous to the planet Odyapes. In addition to that, his name is not actually Billy but "Eeeach Koo-koo-koo Yia", which is rather difficult to pronounce by most. Despite only being seven years old, his species only lives to be 16, making him older than he actually seems. He's enthusiastic and gets along well with his other pilots, but harbors resentment against those that make fun of his running.
One of his ancestors was the first monkey (of his species) to enter space and was a trained rocket pilot. His species seems to not be specially intelligent, since he himself was trained in a laboratory in linguistic skills and eventually to enter the F-Zero races. He's since competed for two years, though he has yet to win the Grand Prix. In the anime, Billy is a member of Dark Million who betrays them.
- In F-Zero GX, the character AiAi, from Super Monkey Ball appears on Billy's belt.
|Introduced in F-Zero|
|Captain Falcon - Dr. Stewart - Pico - Samurai Goroh|
|Introduced in F-Zero X|
|Antonio Guster - Mrs. Arrow - Baba - Beastman - Billy - Bio Rex - Black Shadow - Blood Falcon - Dr. Clash - Draq - Mr. EAD - Gomar & Shioh - Jack Levin - James McCloud - Jody Summer - John Tanaka - Kate Alen - Leon - Michael Chain - Mighty Gazelle - Octoman - Roger Buster - Silver Neelsen - The Skull - Super Arrow - Zoda - Super Falcon (through cheat code)|
|Introduced in F-Zero: Maximum Velocity|
|Megan - Mickey Marcus - Jane B. Christie - Nichi - Lord Cyber - Alexander O'Neil - Blitz Wagner - Kent Akechi - Kumiko - Professor Yazoo Jr.|
|Introduced in F-Zero GX/AX|
|Phoenix - Princia Ramode - QQQ - Don Genie - Terry "Digi-Boy" Getter - Dai Goroh - Dai San Gen - Lily Flyer - PJ - Deathborn - Spade|
|Introduced in F-Zero: GP Legend|
|Rick Wheeler - Lucy Liberty - Misaki Haruka - Lisa Brilliant|
|Introduced in F-Zero Climax|
|Berserker - Clank Hughes - Death Soldier|
| Racer #10|
| Racer #11|
| Racer #12|
|Characters of F-Zero|