Timon targets a strong bug to eat while Pumbaa acts like a hippie to prevent Timon from catching it.
"One Tough Bug" begins by introducing Timon, a meerkat, and his warthog friend, Pumbaa. At the start of the episode, Timon and Pumbaa are visiting the Amazon, eating bugs while on their trip. The two then run into a strong bug, who beats them up, calling it "the Big Bad Bug of the Amazon." Timon reads a book that says that the strong bug has never been caught and eaten, making the meerkat suggests that he and Pumbaa should be the first ones to consume the Big Bad Bug.
The bug lies down on a tree, which Timon sneaks behind and is about to eat the bug. But the Big Bad Bug manages to escape Timon's hand and beats the meerkat up again. The Big Bad Bug is now swimming at the Amazon River. While Timon makes on how he and Pumbaa can catch the bug, Pumbaa suggests that they should just leave it alone, because it might have something to live for. But Timon disagrees and he puts on a swimsuit and catches the bug, who beats Timon up. After Timon gets back on the shore, Pumbaa states that the bug is living a precious life, but Timon persists on catching and eating it.
Timon tries another way to catch the bug, this time by using a net and a bear trap. The plan, however, fails as the bug captures Timon with a bigger net. While Timon looks for another way to catch and eat the Big Bad Bug, Pumbaa, now dressed as a hippie, tells Timon to leave the bug alone and live in peace and harmony, but Timon tells his friend that the bug is evil and it will spread it until all bugs have turned against them. He shows Pumbaa that a video showing that there are more bugs than mammals in the world and tells him that it one bug stands up to them, so will all the other bugs.
While Timon, dressed as a military sergeant, attempts to destroy the Big Bad Bug with a tank, Pumbaa demonstrates against the meerkat's war and the two argue over who believes in their causes the most. While the meerkat continues his attempt, the bug destroys the tank, making Timon's plan fail again.
Timon now uses a helicopter to shoot the bug with missiles, but they miss the insect. The bug is now about to eat the helicopter, making Timon quickly launch himself out. The meerkat now uses a cannon, which the bug eats as well. The bug then turns itself into a butterfly, causing Timon to change his heart and tell Pumbaa that he was right about the bug having something to live for.