At an Agricultural Expo, microbiologist Farmer Brown presents a giant sheep he created with growth hormones, proposing that giant animals could solve world hunger. However, the flashing cameras startle the sheep and it goes on a rampage. Farmer Brown goes to court for the incident and the judge orders him to end his experiments and move his creatures out of Gotham. Farmer Brown protests that he'll be ruined but the judge shows no sympathy. Farmer Brown vows revenge.
A year later, Bruce Wayne is on a date, when suddenly giant praying mantises attack the city. Bruce slips away and arrives as Batman to fight the giant bugs. He sprays them with pesticide but to no avail. The mantises corner him, but suddenly fall apart.
In the Batcave, Batman analyzes the head from a mantis with Batgirl and Robin. They discover the insects' DNA was altered to be immune to poisons and they were engineered to self-destruct. Batman knows there is worse to come.
At Farmer Brown's farm, his daughter, Emmylou, tells him the livestock will be ready to "go to market".
A giant cow and bull attack Gotham as Batgirl and Robin try to fight them off. At the same time, Batman deals with giant, Velociraptor-like chickens. Batgirl and Robin defeat the cow with a bola and get the bull to crash into a building. Meanwhile, Batman catches two chickens in nets. The last one crashes into a vat of hot sauce.
At the Gotham Police Department, Batman tells Commissioner Gordon that he suspects Farmer Brown is behind this. A genetically engineered talking goat arrives and demands a $50 million ransom at the docks.
Harvey Bullock arrives with the money but grabs a rope from the boat and makes it to Farmer Brown's hideout, but Emmylou catches him and throws him to a mutant pig. Farmer Brown discovers the money is fake and has a bat tracer on it. Batgirl and Robin show up and save Bullock but Emmylou defeats them. Batman arrives to fight Farmer Brown. Batman almost wins until Farmer Brown threatens his partners with an electrified pitchfork.
Farmer Brown locks them in a silo that is actually a rocket filled with hatching giant mantises. The rocket sets off but Batman tricks a mantis into breaking the door open and they escape. Batman drives a truck into the silo and it blows up. The rocket takes off but explodes, destroying the bugs.
The police arrest Farmer Brown and Emmylou.
- Big Creepy-Crawlies: Farmer Brown threatens to release a scourge of giant mantises on Gotham if they don't give him 50 million dollars.
- Bio-Augmentation: Augmented farm critters and pests, including giant bugs preprogrammed to 'die' after a particular length of time. Originally microbiologist Farmer Brown was only out to augment cattle and other farm animals to provide more and better food; a PR event gone awry resulted in a court ordernote preventing him from experimenting in Gotham. So Brown & daughter move to extortion by threat of bio-augmented monster animals.
- Canon Foreigner: Farmer Brown
- Cut Lex Luthor a Check: Farmer Brown initially wanted to use his research for peaceful means, then turned to supervillainy when his practices were outlawed.
- Disastrous Demonstration: Farmer Brown's demonstration of giant farm animals goes awry when the giant sheep he's presenting breaks out of its cage. The idea behind the giant animals was to create a means to end world hunger, but because of the incident Farmer Brown was ordered to stop his work. Which led to him becoming the villain of the episode.
- Disproportionate Retribution: Farmer Brown takes revenge against Gotham for forcing him to shut down his experiments and calling his creations "monsters".
- Does Not Like Shoes: Emmylou
- Donut Mess with a Cop: A talking goat steals Harvey Bullock's doughnut from under his nose.Bullock: Hey!, He ate my donut!!
- Even Evil Has Loved Ones: Farmer Brown and Emmylou may be ruthless criminals but they still love each other as much as any normal father and daughter do.
- Face of an Angel, Mind of a Demon: Emmylou could practically be an Expy of Daisy Duke, but she's as brutal and merciless as her father.
- Farmer's Daughter: Emmylou Brown, who, thanks to some "Beef Steroids", doesn't go down easily.
- Fed to Pigs: Combined with Fed to the Beast; Almost happens to Bullock when Emmylou throws him to a boar that has been genetically modified, likely to be carnivorous.
- Fluffy Tamer: Cranked Up to Eleven with Farmer Brown's daughter Emmylou and his genetically-modified farm animals.
- Getting Crap Past the Radar: After Batgirl and Robin take down a genetically modified giant cow:Robin: That's a lot of bull.
- I Will Show You X: "Monsters? I will show them monsters."
- Muscles Are Meaningless: Emmylou is very thin, but able to effortlessly lift and throw Harvey Bullock, and doesn't even budge when Batgirl lands a leaping kick on her chest.Emmylou: Beef steroids.
- Obligatory Joke: Robin and Batgirl are fighting genetically altered giant cows. Batgirl lampshades the fact that Robin couldn't resist yelling "Holy Cow!"
- Offscreen Villain Dark Matter: In the DVD Commentary, the show's producers cannot figure why Farmer Brown would be demanding payment from the city: the weapons and equipment he uses during the episode must have cost millions, so he must have found a way to make money anyway. Or he could have easily stolen them.
- Oh, Crap!: Barbara gives a worried "Oh boy" after her flying kick bounces off Emmylou's chest.
- Should Have Thought of That Before X: When Farmer Brown pleads that shutting down his experiments will ruin him, the judge says "You should have thought of that when you started creating these monsters."
- Shout-Out: Bullock refers to Farmer Brown as Jed Clampett.
- Southern-Fried Genius: Farmer Brown
- Talking Animal: Farmer Brown sends a mutant talking goat to deliver his message to Commissioner Gordon.
- Trick-and-Follow Ploy: Used by Batman to find Brown; Emmylou clearly isn't as Genre Savvy as her dad is.
- Visual Pun: At one point the mutant bull smashes into a china shop.