- "Frank thinks he's one tough dude, but if you're fairly experienced, he won't give you much trouble. Be sure you're well-supplied when you face him."
- — Earthbound Player's Guide
Frank is a young man with light blonde hair, a square jaw, a straight nose, pearly white teeth, and high cheekbones with hollowed cheeks. Both his clay model and battle sprite sport wide, toothy grins. His hair seems to be a mix between a shark-fin-shaped Mohawk and a mullet.
Frank wears a dark red, double-breasted pinstripe suit, a dress shirt with cuffed sleeves, black dress shoes, a pair of black sunglasses, and a shark tooth necklace.
Both his clay model and battle sprite depict him wielding a pair of daggers.
- "Fail-proof Frank can't be beaten."
- — Frank Fly
Frank is a ruthless yet misguided youth, as he was able to take over Onett with the help of his own gang, the Sharks. His influence was so great that Onett's police force did not try to arrest him or his gang, hinting at the police force's ineffectiveness. Because no one prior to Ness thought to challenge him in a fight, Frank saw himself as "fail-proof". Once he was defeated by Ness, however, he called himself "Failure Frank" in light of his loss.
After he is defeated by Ness, Frank has a positive change of heart and disbands the Sharks. In an attempt to shape himself up, he takes a job at a Burger Shop, where Ness can talk to him afterwards to recover HP and PP. During the Chosen Four's final battle with Giygas, Frank is one of many people who prayed for the safety of Ness and his friends, which played a role in Giygas' final defeat.
He seems to be talented with machines, as he built his own robot, Frankystein Mark II.
Prior to the events of Earthbound, Frank Fly formed the Sharks and took over Onett, terrorizing the small town and causing many of its residents to move to Twoson. He then established his gang's headquarters at the local arcade.
Frank would later vandalize the Traveling Entertainer's Shack, causing it to be closed and depriving Ness of a way into Giant Step. At the request of Onett's mayor, B.H. Pirkle, Ness confronts Frank in the backyard of Onett's arcade and ultimately defeats him. Unwilling to admit defeat just yet, Frank sends in his robot, Frankystein Mark II, to take care of Ness, who wrecks it.
Frank then finally sees he's been bested and accepts it, calling himself "Failure Frank". He proceeds to tell Ness about Giant Step, explaining it contains some kind of mysterious power. He then disbands the Sharks gang and gets a job at a Burger Shop in an attempt to shape himself up. Ness and his party can talk to him in order to recover lost HP and PP.
Frank is later seen near the end of the game, being one of many people who answers Paula's prayers for help against Giygas. He prays for Ness' safety, which plays a role in weakening Giygas and allowing him to be defeated by the Chosen Four.
After Giygas' defeat, if Ness visits Frank again afterwards Frank will welcome him back and show interest in any story Ness might have about his adventures.
- Brandish a knife - Frank uses his knives to attack a party member, dealing high damage.
- Come out swinging - Frank uses his fists instead of his knives to attack a party member, dealing low damage.
- Say something nasty - Frank will say demeaning words to a party member, lowering their Guts for the duration of his boss fight.
- Frank's equivalent seems to be Teddy from Earthbound Beginnings. Both men are misguided gang leaders who terrorize the cities they live in (Ellay and Onett, respectively), but after they are defeated by the protagonist (Ninten/Ness), they see the error of their ways and support the protagonist. In addition, both Frank and Teddy wear sunglasses, wield knives, and have the Hippie's theme as their boss theme. Unlike Frank, however, Teddy is an optional playable character who can be recruited into the main party, and his weapons can be upgraded to swords.
- It is implied that Frank is either in his teens or early twenties, as he says he's still "underage" when you talk to him after defeating Giygas.
- "So you made it back alive. You must have many stories to tell. Let's get together for a drink, when you have a chance so I can hear your stories. ...I'm talking about drinking mineral water. I'm still under age, you know."
- — Frank Fly's Dialogue after defeating giygas.