Details about his past are sketchy, but he has known Keenan since he was very young, and has a distrust of humans other than Keenan. He and Keenan were protected by a female Frigimon—who was destroyed—an act which Falcomon believes humans are responsible for.
Digimon Data Squad
Years after this, he came to the human world on his own to try and return Puwamon to the Digital World. In his second attempt, he showed great speed and prowess, until he was knocked out of the sky by Marcus Damon. He was nearly destroyed by GeoGreymon, until Merukimon arrived to save him. He then returned to the digital world. He was reunited with Keenan, and joined his human partner in ambushing the members of DATS when they came to the Digital World. During his attack on the DATS members, he Digivolved Falcomon to Peckmon.
After this, Falcomon's next prominent act was to forge an unsteady alliance with the humans, in order to save Keenan from the virus that was afflicting him and Yoshino "Yoshi" Fujieda. He led them to a place called Wanderer's Cape, where they were beset by a Blossomon sent by the Gotsumon that works for Merukimon. Falcomon escaped with the vaccine and helped Keenan, but also helped to save Yoshino. He departed with his partner, conflicted in his thoughts about humanity. He and Keenan attacked again near Merukimon's lair only to be interrupted by a Mammothmon unleashed by Gotsumon. As Gawappamon was holding off Merukimon, Falcomon followed the DATS members (and the unconscious Keenan) back to the Real World. After Okuwamon attacks and Hagurumon taking over Dr. Crier's house, Falcomon fled with Keenan when Commander Sampson's superior Chief Hashiba appeared. Falcomon continues to help Keenan and DATS. After the fight against Yggdrasill, Falcomon returns to the Digital World with the other Digimon.