Forbidden Fruit is the fifth episodes of the Beast Machines TV series.
In the depths of Cybertron, the two technorganic warriors, Blackarachnia and Cheetor, mock-spar in their beast modes. They are being tutored by Optimus Primal on finding their still point during battle so they can transform. Cheetor objects to the new, "mystical" Optimus and proclaims that he trusts his instincts. All this unfolds while they are watched by an unfamiliar set of bat eyes. Beside the more advanced Blackarachnia and Cheetor, now learning to transform in combat, Rattrap is still struggling with the basics of his technorganic body and relearning the transformation process—unsuccessfully. Optimus Primal tells Rattrap to have patience and just let it happen. Frustrated with his new body and his liability in combat, the rat lashes out at his leader. According to him, Primal should save his advice for the still-missing Rhinox and Silverbolt.
Hurt, Optimus Primal leaves Rattrap, while the other two scold the rat for his behavior. Primal notices something up above and catches it. It's a bat, and Primal is shocked at the presence of organic life on Cybertron. Before he can examine it further, he is hit with a sonic pulse, and the creature flaps away. The Maximals pursue the bat in their beast modes through the lower regions of Cybertron before Cheetor transforms and catches the creature. As Cheetor holds the bat down, it speaks! Not only that, it—or rather, he—claims to be a Maximal.
At this point, Jetstorm and his Aero Drones appear and attack the Maximals. Optimus Primal, Cheetor, and Blackarachnia transform into combat modes, while Rattrap, unable to transform and devoid of weapons, hides. After a short clash, the Maximals run away, followed by Jetstorm, who fires a homing mine after the Maximals that the bat deflects with a sonic blast. While the Maximals take cover, the Aero Drones are destroyed by the bat, and Jetstorm vows to return.
The creature, being the kind soul he is, leads the Maximals back to his hideout. On the way, Optimus Primal tells him a simplified story of the Beast Wars, their reformatting, and basically all the events leading up to the present. The bat recounts how he found himself trapped in this new form when the first Vehicon drones attacked Cybertron. As other robots were destroyed, he fell down a deep pit and awoke, he says, in his current, organic body. When the Maximals reach their destination, Primal is amazed at the bat's temporary home. It is a towering, organic fruit tree lodged in the metal world of Cybertron.
The creature explains that he has been eating from the tree since his transformation and offers its fruit to the others. While three of them accept, Cheetor is suspicious of the creature. While Optimus Primal tries the fruit, claiming that it may help their organic components, Cheetor retorts that he only processes energon, period. Cheetor interrogates the bat and demands answers. He wants to know if the newcomer's an agent for Megatron, but the bat denies it, as Megatron took everything he loved away from him. Cheetor and the bat go back to the others, but the Maximals seem unresponsive and strange. Primal beats his chest and speaks in a primitive way, while Rattrap and Blackarachnia squabble over the fruit, hissing and nipping one another. The organic fruits have magnified their bestial sides, creating a mental imbalance and the eventual dominance of their animal natures.
Amidst the chaos, Jetstorm reappears and attacks. Cheetor attempts to snap the others out of their beast mentality and get them transform. They ignore him, and he and the bat attempt to take the food away from the increasingly feral Maximals. Cheetor notices the trunk of the organic tree, transforms, and cuts it down, despite the bat's protests. This restores the affected Maximals to their old selves, and they transform and begin the fight. The bat is badly hurt by a blast from Jetstorm, and the only way to save his life is for Optimus Primal to reformat him.
From his chest, a brilliant white light shoots out. The bat's organic components are mixed with technology, and a technorganic bat emerges. Transforming into his new robot mode, he decimates the ranks of the Aero Drones and drains energon out of Jetstorm until the general crashes. But reformatting the creature has taken its toll on Optimus. He is severely weakened and requests Cheetor to lead while he recovers, as Cheetor was right to destroy the tree; its purely organic nature was creating imbalance in their technorganic bodies. Cheetor eagerly accepts and orders Optimus to be placed on a stretcher.
The new robot decides to travel with them and introduces himself as Nightscream. But as they leave, a fruit from the organic tree puts down roots into what appears to be organic soil!