The Buster Machine FS-0O Frog is an auxiliary support machine from the Japanese series Tokumei Sentai Go-Busters (2012). Rather than belonging to the core five Buster Machines, it is a supplementary, movie-only mecha: it was built by Masato Jin (Beet Buster) and ranks among his early first-generation prototype units. Its designation FS stands for Frog Submarine, i.e. a submarine-type machine with a frog motif. It debuted in the 2012 summer film Tokumei Sentai Go-Busters The Movie: Save the Tokyo Ene-Tower!. Because the US adaptation Power Rangers Beast Morphers (2019–2020) never adapted the theatrical film, the FS-0O received no Power Rangers name and was never released as a Power Rangers toy — making it Japan-exclusive.

Like the other Buster Machines, the FS-0O switches between a Buster Vehicle Mode (a submarine with powerful underwater headlights, attack missiles, a personnel bay and an observation deck) and a Buster Animal Mode, the actual FS-0O Frog. In animal form its signature feature is a boxing-glove tongue, a tethered striking weapon that shoots out as a projectile. For ground combat it forms a special combination: when the FS-0O Frog takes the place of the RH-03 Rabbit in the Go-Buster Oh formation, it joins with CB-01 (Go-Buster Ace) and GT-02 Gorilla to become Go-Buster Kero-Oh. This robot carries so-called Ene-tan Screws on both arms (firing tornado-like beams) plus a launcher for Tadpole missiles.

The DX toy was released in 2012 by Bandai (Japan) alongside the film. It converts between Vehicle and Animal modes and combines with the separately sold DX Go-Buster Ace (CB-01) and GT-02 Gorilla to form Buster Kero-Oh. The set includes the torpedoes/missiles as firing accessories. It is a predominantly plastic transforming-and-combining Zord from the DX line; no significant die-cast content is documented. No Bandai America or Hasbro version exists — the FS-0O Frog remained exclusive to the Japanese Go-Busters line.