Zero the Kamikaze Squirrel is a spin-off of the Aero the Acro-Bat series. The main star is Zero, Aero's rival from the previous games.
The plot begins halfway through the plot of "Aero the Acrobat 2". Zero receives a note from his girlfriend Amy that evil lumberjack Jaques Le sheets is destroying his forest homeland in order to use the trees for printing money. Zero, despite the protests not to do it from his master Edgar Ektor (who tells him nothing is more important than his mission with him, notably referring to Ektor's plan B from Aero 2), decides to return home and stop Le Sheets (which explains why Zero is absent from Ektor's side in the Aero 2 final battle). When arriving his home island, Zero's plane is shot down and crashes on the beach, so he must make his way to the forest on his own. Zero's path takes him through caves where he faces creatures from the dark, a volcano where he defeats mining workers and guard robots, a river he must go through in his own jet ski, the forest where he defeats the metal claw-wielding guardian, a boat ride through a toxic waste sewer and finally Jaques Le Sheets money paper factory. After a confrontation where he finally defeats the evil Jaques Le Sheets Zero spots a flying ship trying to escape, which he manages to board just in time. There he finds out it was all a plan from his own master Edgar Ektor (it is left to the player to assume that this was his fool-proof back up plan referred in the ending of Aero the Acrobat 2). While holding Amy hostage, Ektor faces Zero in a final battle. In the end, with assistance from Amy, Zero is able to defeat his evil master and leaves him aboard his own flying vehicle to crash on the beach. For the last time Zero is seen falling victorious from the ship in a parachute while carrying Amy in his arms.
A version for the Game Boy Advance was planned in 2003, but it was never released.
Source: Wikipedia, "Zero the Kamikaze Squirrel", available under the CC-BY-SA License.