Bender and Fry volunteer for military duty to enjoy the benefits of the soldiers' discount. Leela attempts to join as well, only to discover that women are not allowed to join the army. she decides to sign up as Lee Lemon, becoming one of the best soldiers in the troop. Of course, not even her disguise can stop her commander, Zapp Brannigan, who begins feeling uncomfortably attracted to Lee. Meanwhile, a war breaks out, and Bender, Fry and Leela are sent out to a mysterious planet, inhabited by bouncing balls. During a battle, Fry proves to be a coward, hiding in a hole, while Bender becomes a hero when a bomb is rolled into the middle of their group and he sacrifices himself by covering it up with his body. Back in camp, while Bender is rewarded for his service, being repaired and promoted, Fry is punished. Zapp Brannigan decides to give Fry the most degrading job he can think of. Not Zapp's assistant, but Kif's assistant!
After trying to tempt Lee/Leela in the shower house, Zapp gives Bender an important mission: to go meet with the brain balls, leaders of the natives, and try and make peace. As Bender flies off, Zapp surprises Leela and Fry by ordering an evacuation. He reveals that he planted a bomb in Bender during the repairs, and the bomb is activated by Bender's most commonly said word: ass. Fry and Leela set out to rescue Bender and keep him from saying the a-word.
Meanwhile, on Bender's side, we watch as the peace talks come to a stalemate and Bender comes perilously close to saying ass multiple times. Fry and Leela burst in and warn Bender. However, Bender uses this peace talk to force the Brain Balls to agree to his demands, and drives them away from their home planet, much to the concern of Fry and Leela. Bender is eventually subdued. Back on Earth, Bender wakes up to find that while the Professor could not deactivate the bomb, he changed the code word to one of Bender's least said words, and he refuses to tell Bender which word it is. Bender spends the last few seconds of the episode trying to figure it out, the word: antiquing!