Beni Beni was the Monster of the week in Ep.58 of the Grendizer Anime and was the 63rd Beast in the series overall. Resembling a Bipedal Lizard, it had the head of a mouse with whiskers and big pointy ears, with humanoid hands and white spikes running down the back. The Monster had Green color scheme going from light to dark. It had two light yellow eyes. The Beast, was considered King Vega's Most prize monster.

Beni Beni was agile in combat, fire a beam from its eyes and spew fire from the mouth, but its main talent was shapeshift itself and its pilot into the enemy (in its case Grendizer and its Pilot into Duke Fleed), though the monster remain in control of its function with the pilot just tagging along. This did not gave it all of the Mecha's abilities, outside morphing into the Grendizer Spazer, rather than ejecting, and firing a version of Space Thunder and Hand beams.

Beni Beni was brought to Earth via Capsule crashing into the sea, the Space Observatory detects it and Koji leaves on the Marine Spazer to investigate; the invaders collect the capsule and conceal themselves; finding nothing, Koji is recalled. In the base, Beni Beni is release from its capsule were Zuril and Gandal begin to use its talents for their next plan; using Tablet diagrams of Grendizer and Duke Fleed, both the Monster and an Agent (one of the king's Guard) assimilate the forms of the Mecha and Pilot, in a bid to discredit Earth's protector. Gandal takes off on the Mother Fortress and launches a Midifo armada, which is detected and the rest of Team Grendizer launches in response. Koji takes out some of the attackers when Grendizer shows up, the Armada retreats, with the Mecha on their following them all the way to orbit where it decimate the rest of the Armada; this when the villains spring their trap with magnetic meteors, which cling to Grendizer and their powers begin to cause system malfunction, rendering the mecha inoperable. Beni Beni/Fake Grendizer is launched to continue with the rest of the plan.

The Fake encounters the rest of the team, who notice a bomb in the back of the head, which detonates and the "Mecha" flies out of control, crashing through a Rail Bridge, where a Train and its Passengers fall to their deaths. The team follows it.

Side Note: in a rarity, you get to see a child die here. Train explodes and everything and the kids Doll is carried away by the river.

Then the fake attacks the city causing untold destruction; the rest of the team horrified by the turn of events, with Hikaru visibly distraught, trying to talk to Daisuke; when the two pilots set eyes at each other, Hikaru can tells this is NOT Duke, as the fake's eyes are red, but is shutdown and hurt in the crash. The other Pilots land to assist, the fake changes into the Spazer form and escapes.

At the Observatory, Hikaru is in Med bay unconcious with Umon and the other still flabbergasted, when they learn The Defense Force have been summon to attack Grendizer, seeing how things have turn, Umon agrees, much to the protests of Maria. Koji takes departs on Double Spazer, set out to kill Duke; as the Fake destroys the Defense Force and the City, the Real Grendizer finally escapes from its trap, as the Magnetism in the meteors dissipate and returns to Earth, where it encounters Koji, who fires Double Missiles, hitting the face cockpit and the Mecha Crashes into the woods. As Koji lands Duke exist the Mecha but falls to the floor; Koji, approaches and readies to kill Duke, but is hesitant. Duke stands up, calls to him and demands answers, prompting Koji to drop the gun, thinking Duke has regain conscious.

After everything is explain to Umon, Duke and Koji learned that Maria decided to go out and kill her brother, not knowing the truth yet, the heroes go out to find her; Maria encounters the fake, and much like Hikaru, she sees the situation for what it its and flies away, with villain behind her, she encounters Double Spazer and the Real Grendizer. Duke fires Hand Beam, reverting the Pilot to its true form; Grendizer then smashes the wing of the fake, breaking it, and exposing the true form of the Beast with Space Thunder, making Beni Beni crash.

Now with the Cat (or the Lizard Mouse Gremlin) out of the Bag, the giants fights, Beni blocking Screw Punch, then attempting to rip the Cockpit to get to Duke; The Beast is tossed over, but the monster recovers and fires its Optic Beam, blocking the hand Beam, and tossing Grendizer to a mountain, which the Beast fires at, burying the Mecha in an avalanche. Beni attacks, but its hit by Double Punch, leaving it blind; Grendizer recovers and kicks the monster, then finishes the Beast with Double Harken, disposing of it and the Pilot.

After the battle, Team Grendizer returns home, with Umon and an awaken Hikaru expecting them.