When Digimon Tamers made DNA Digivolution a centerpiece in 2001, it looked brand new. Two partners, one fused monster, a bond that literally combined them. But the mechanic had been sitting in Japanese pockets since 1998 — on a device that never officially got an English release.
That device was the Digimon Pendulum, the direct successor to the original Digital Monster V-Pet, and the quiet birthplace of some of the franchise's most enduring rules.
A fighting pet that needed two players
The original Digital Monster, launched in Japan on June 26, 1997, was built around one novelty: Link two devices and your pets could battle. It was a clever hook, but it had a ceiling. Every Digimon evolved roughly the same way, and once you'd seen one champion stage, you'd seen them all.
Bandai's fix, released in 1998, was a new series of V-Pets called the Pendulums. The name came from pro wrestling — project leader Oota Kensuke named it after the "pendulum backbreaker" move he'd loved as a kid. But the real changes were under the case.
Swing to win, fuse to evolve
The Pendulum traded the original's button-heavy raising for one physical mechanic: a pendulum that counted how many times you swung the device. More swings meant stronger attacks and faster progress — a proto-activity tracker that fit a pocket-size toy.
Two features, though, did the heavy lifting in franchise history.
First, the Pendulum added a sixth evolutionary stage. Above the familiar Perfect (Ultimate in the dub) sat a new Ultimate tier — Mega to Western fans — reachable only through sustained care and, in many cases, cooperation.
Second, and far more important, it gave us Jogress: Joint Progress, or what English audiences know as DNA Digivolution. By linking two compatible Pendulum devices, tamer and friend could fuse their partnered monsters into a single, higher-stage Digimon — and both tamers kept a copy of the result. For the first time, a Digimon's evolution could literally depend on another player. That's the DNA at the heart of Omegamon's casual-team-up in Our War Game and every fused evolution Tamers would later dramatize.
The attribute cycle arrives
Jogress wasn't cosmetic. It ran on a proper attribute cycle — Vaccine, Data, and Virus — the first time the virtual pets enforced a rock-paper-scissors triangle that decided compatibility. Mix two Vaccines and you got a Vaccine; combine a Virus and a Data and you got a Virus. If the attributes didn't match, the fusion just failed, an error flashing on screen.
That single mechanic quietly set the template for Digimon's battle system for the next two decades.
Five waves, one colossal legacy
Bandai shipped five main Pendulum versions — Nature Spirits, Deep Savers, Nightmare Soldiers, Wind Guardians, and Metal Empire — each followed by a half-step update with a tweaked roster, plus a special Virus Busters (Version 0) that finally put War Greymon and Metal Garurumon in players' hands and let them Jogress into Omegamon.
The Pendulum never hit Western shelves officially, which is why so many fans met its innovations first through the anime. But play one today and you'll feel the blueprint: the attribute triangle, the fusion evolution, the Mega tier that made a partner's final form a goal worth growing for. DNA Digivolution didn't start with a TV show. It started with two kids swinging a toy in a Japanese park, betting their monsters could become something greater together.