Mayor Manx and Callie Briggs unveil the 300 story Megakat Tower, showing it to Siamese businessman Mr. Young (Robert Ito) and his associates, hoping that they'll buy office space in it. Also present are Ann Gora and her cameraman Jonny. Young refuses to commit just yet, and so Manx invites him to come play golf with him while he thinks it over. At the SWAT Kats' hangar, Chance is playing an arcade game called Space Kat. He is interrupted by Jake, who has recently taken up gardening as a hobby, filling the hangar with potted plants. Distracted by Jake watering a fern, Chance loses the game, but Jake assures him "there's always another universe to save."
At the Megakat Tower, a suspicious-looking gardener with green fur is going around watering all the plants, and makes a point of hiding his face as Callie, Ann and Jonny get off the elevator to leave. Although the reporter and cameraman leave, Callie notices the gardener behaving strangely and decides to follow him. Outside, giant vines suddenly erupt through the concrete and grow up the side of the building as Ann and Jonny watch in horror.
In the basement, the gardener reveals himself as none other than Dr. Viper, having survived the destruction of Megakat Biochemical Labs. His latest creations, mutant plant creatures called Plantimals, have completely taken over the building. Callie contacts the SWAT Kats, but she barely manages to do more than tell Chance that Dr. Viper is back and has taken over the Megakat Tower before vines grab her and take her prisoner. Chance and Jake suit up as the SWAT Kats and fly off to the rescue.
At the Megakat Tower, Commander Feral is informed what happened. He, Burge and King try to take the building from above using their choppers, but they're attacked by flying Plantimals that spit acid, damaging their choppers, forcing the Enforcers to retreat. In the penthouse, Callie is held prisoner by a Plantimal as Dr. Viper explains that his plan is to use a pulsating "spore pod" to shower Megakat City with mutagenic spores, turning it into a festering, mutation-filled wasteland he wants to call "Megaswamp City." The SWAT Kats arrive, but the flying Plantimals prove impervious to everything thrown at them. Callie escapes by hitting her Plantimal guard with a typewriter, but she's still stuck inside the building, so Razor decides to break in to find her and stop Dr. Viper.
Act II
Using his Ejektor seat, Razor breaks through a window on the 145th floor. He explores the floor, fighting various plant monsters, including mutated cacti that fire their needles as projectiles. Like their airborne cousins, the Plantimals Razor encounters inside the building (called "Rovers") prove nearly impossible to kill.
Outside, Feral orders Peacekeeper tanks to shoot at the wall of vines blocking the entrance. They succeed, but a giant Plantimal called the "Behemoth" emerges and blocks the door. It sprays acid at the Enforcers. One Peacekeeper sinks into the acid, but its crew manages to bail out. Mayor Manx, having observed what was going on from afar at Megakat Golf Course, contacts Feral by mobile phone and forbids him from taking any further action which could damage the building, despite Feral's pleas, telling him he is only allowed to use weed killer.
Inside, Razor uses electrical grenades to fry the Plantimals, but even that fails to kill them. Using a buzz-saw weapon, he cuts a hole through a wall to escape. Finding himself in a law office, he pushes a bookcase over the hole and encounters Callie. The Plantimals bust down the flimsy bookcase barricade and enter the office. To get away, Razor and Callie climb into an air vent. As they scramble in, Razor's toe hits the thermostat, turning the air conditioning on.
Back outside, Sergeant Talon informs Feral that Burge and King have arrived carrying a thousand gallons of weed killer aboard their chopper. They drop the tank onto the Behemoth, but it has the opposite effect of what they'd hoped. As Feral and Talon watch in horror, the already huge Plantimal only mutates and grows larger. Feral is so enraged he snaps his baton in half. Back inside, Callie informs Razor of Viper's plan as the two crawl through the air duct. Suddenly two Rovers burst through the floor and move to attack them.
Act III
A gush of cold air from Razor having accidentally turned on the AC hits the Rovers, freezing them solid, and Razor is able to shatter and kill them. He and Callie realize cold is the creatures' weakness. When Callie suggests freezing the entire building, Razor contacts T-Bone, telling him to retrieve super rocket coolant from MASA, Megakat City's space research center. Then he and Callie enter the elevator shaft of the building and begin climbing, briefly menaced by a giant Plantimal climbing up after them.
At MASA, T-Bone convinces two technicians (Frank Welker and Richard Gilbert Hill) to give him "enough coolant to freeze a whole city block," and hurriedly flies back. At the Megakat Tower, Razor and Callie escape the Plantimal chasing them up the elevator shaft and come out onto the roof, where the spore spod has outgrown the penthouse and is beginning to swell to the point of bursting.
Razor confronts Dr. Viper, and Viper uses his tail to smack Razor off the roof, seemingly to his death. He then orders three Rover Plantimals to kill Callie. Just as they're about to strike, Razor rises up into view standing on the back of the Turbokat, and helps Callie aboard. T-Bone banks away just as the three Rovers try to jump on, too, and the monsters fall to their deaths.
Dr. Viper sends the flying Plantimals after the heroes, and their acidic spit damages Razor's targeting system, preventing him from dropping the tank of rocket coolant from inside the cockpit. He has to climb down and decouple it from the jet by hand. It falls towards the building. Dr. Viper screams and tries to run but the tank hits the roof and the spore pod and explodes, sending up a huge freezing cloud of mist. The freezing air rushes through the Megakat Tower, freezing all of the mutant plants. The Enforcers retreat to safety, but the Behemoth isn't as lucky; it's frozen and then shattered by falling debris from the explosion up above.
The SWAT Kats land, and Callie thanks them for their help. Razor jokes that after this he's going to give up gardening, and then he and T-Bone fly home. Manx and his prospective buyers return from golfing to find the skyscraper a twisted, thawing ruin. Mr. Young declines the Mayor's offer as politely as he can, and then he and his fellow businessmen depart, a sputtering, pleading Manx hurrying after them.
Tropes featured in this episode include:
- Absurdly Ineffective Barricade: The bookcase Razor pushes over the hole in the wall. The Rovers bust through it in no time.
- Acid Attack: The Flyers spit acidic loogies at their enemies, and the Behemoth has tentacles on its back that hose down targets with acid strong enough to melt tanks "like butter."
- Air-Vent Passageway: Razor and Callie escape from the Rovers in the law office by going through the ventilation system. As in Die Hard, it's realistically proportioned on the inside for the most part.
- Alien Blood: A deleted scene from the script reveals that the Rovers have acidic blood, when one splatters onto and melts Commander Feral's cruiser.
- All There in the Script: The names of the individual Plantimal types, the main sergeant (Talon) and the two pilots (Burge and King). In addition, this episode's script retroactively made Burge and King the two Enforcers at the beginning of "The Pastmaster Always Rings Twice."
- Angrish: Manx upon discovering the thawing ruin of his beloved building. A rough attempt at a translation of the noises he makes would be as follows:Manx: [gasps] Criminy! I can't believe—Wha-Haaaaaaa...
- Artistic License – Engineering: The Megakat Tower is stated to be 300 stories tall. This is several hundred stories taller than the actual tallest building currently in existence, the Burj Khalifa in Dubai, which is "only" 160 stories. Wind and the building's weight would make a 300 story tall skyscraper a structural impossibility, especially back in 1993 when the episode was written.
- Big "NO!": Callie, when Razor is knocked off of the roof.Callie: Razor! Noooooo!Viper: Yesss! But don't worry, Ms. Briggsss! You'll be joining him!
- Captain Obvious: Well, Sergeant Obvious. Most of Talon's dialogue in this episode is just to point out what's obviously happening onscreen.
- Chekhov's Hobby: Averted. Jake suddenly being into growing plants doesn't come into play except tying into the fact the episode is full of plants.
- Corrupt Politician: Implied with Callie mentioning that Manx used city money to build the Megakat Tower.
- "Die Hard" on an X: This episode is basically Die Hard with plant monsters.
- Disney Death: Razor is knocked off of the roof. The episode milks his supposed death for about two seconds before he rises back up on the Turbokat like Marty McFly on the De Lorean in Back to the Future Part II.
- Disney Villain Death: When Razor helps Callie onto the Turbokat at the end, three Rovers try to leap on after them right as T-Bone pulls away from the building, so all that happens is that the trio end up falling to their deaths.
- Does This Remind You of Anything?: Viper constantly stroking the pulsing spore pod that's going to burst and shower Megakat City with "seed" and calling it beautiful. The two even "get a room" insofar as once they're left alone, he tells it, "It's just you and me now, sssweetnesssss."
- Does Not Know His Own Strength: Feral throwing his walkie-talkie down so hard that it shatters like glass. Even Sergeant Talon is astonished, looking at his own walkie-talkie as if to say, "How did he do that?!"
- Dramatic Shattering: Upon finding out that he cannot do anything to endanger the Megakat Tower, Feral throws his walkie-talkie down so hard it breaks apart.
- Eye-Obscuring Hat: As part of Dr. V's Paper-Thin Disguise.
- Garden of Evil: What Viper turns the Megakat Tower into.Feral: Dr. Viper has turned your pet skyscraper into a living weed patch!
- A Glass in the Hand: Feral snaps his baton in half out of anger.
- Green Thumb: Dr. Viper, by way of his growth formula.
- Hates Being Touched: Subtly implied when Manx puts his arm around Young's shoulder at the beginning. Young tenses, looks at Manx, then looks at his business partners offscreen as if to say, "Why is he touching me?"
- Improvised Weapon: Callie. She escapes the Rover who's guarding her by clobbering it with a typewriter (offscreen), and later, mistaking Razor for a monster (for... some reason), she bashes him over the head with a pot.
- Janitor Impersonation Infiltration: Dr. Viper disguises himself as a gardener to pass (almost) unnoticed in the Megakat Tower, and all the "water" he's pouring onto the plants is actually tainted with his growth formula.
- Japanese Politeness: The Siamese businessmen live this trope, especially at the end.
- Kill It with Ice: The Plantimals' only weakness is cold. It affects them so strongly that a gush of cold air from an ordinary air conditioning vent freezes them solid enough to be smashed apart.
- Lighter and Softer: Dr. Viper comes off as a lot more humorous and Affably Evil in this episode compared to his utterly sadistic behavior back in "The Giant Bacteria." Also, the episode itself follows hot on the heels of nobody dying in "The Wrath of Dark Kat" except Creeplings by having no kats get killed, or even implied to have been killed, except for Dr. Viper (and even he comes back). But besides him, the only deaths are Plantimals.
- Literal Cliffhanger: After Razor uncouples the rocket coolant tank from the jet, he's hanging on to the dangling cable. A pursuing Flyer splats an acid loogie that melts through it, and Razor has to leap up into the open bomb bay, clinging to the edge with his claws to avoid falling to his death.
- Literally Shattered Lives: Several of the Plantimals that get frozen also shatter as a result, particularly the two Rovers in the air vent and the Behemoth at the end.
- Make My Monster Grow: The already huge Behemoth grows even bigger (and spinier) when doused with industrial-strength weed killer.Talon: Commander! Weed killer only makes it bigger!
- Man-Eating Plant: Viper grows one in the basement. Another chases Razor and Callie up the elevator shaft.
- Match Cut: From Jake watering his potted plant in the hangar to the disguised Dr. Viper doing the same in the Megakat Tower lobby.
- Mayor Pain: Manx. Again. This time, he refuses to allow Feral to retake the Megakat Tower unless he can do it without damaging it any further, severally handicapping the Enforcers. Evidently he cares more about his "pet skyscraper" than the fate of Megakat City.
- Oh, Crap!: Viper as the tank of rocket coolant is falling towards him.
- Offscreen Moment of Awesome: How Callie managed to get away from the Plantimal guarding her.
- Paper-Thin Disguise: Dr. Viper's gardener outfit is hilarious, and only fools people from a distance. The most hilarious part is how he hides (or tries to hide) his huge snake tail: he just stuffs it down the back of his pants, giving him the appearance of having a really huge butt.
- Plummet Perspective: When Razor pushes the vent cover off the Air-Vent Passageway, we get a good shot of just how far down into the elevator shaft it falls.
- Put on a Bus: This is the second and final time Burge and King appear.
- Reasonable Authority Figure: Commander Feral. He knows that the stakes demand they take the building back and stop Viper, no matter the cost, or Megakat City is doomed, but Mayor Manx won't let him do anything to damage the structure any further.
- Riding the Bomb: Razor, willingly this time. Because he has to drop the tank of rocket coolant by hand, he stands on the top of it going "Wahoooooooooo!" as it's being pulled through the air by the Turbokat. Subverted in that he does not remain on it when uncoupling it from the jet to fall on the spore pod.
- Roar Before Beating: Viper gives a hearty "Rawwwrrr!" before leaping at Razor in the finale.
- Saved by the Platform Below: Similar to the scene in Back to the Future Part II, Dr. Viper knocks Razor off the roof, only for him to rise up standing on the Turbokat, T-Bone having caught him as he fell.
- Spike Shooter: Some of the plant creatures are killer cacti that fire their own spines.
- Stab the Salad: Chance is introduced in an intense, underlit closeup, telling someone they're dead meat, then he punches the camera, only for it to then be revealed he's playing a video game and just really, really into it.
- Tail Slap: Viper uses his Prehensile Tail to knock Razor off the roof, seemingly to his death.
- Take My Hand!: One Enforcer pulls another up to safety when their Peacekeeper tank is sinking into the acid.
- Tanks for Nothing: The Peacekeepers don't fare any better here than they did in "The Wrath of Dark Kat."Talon: The toughest tanks we have and that—that thing melted 'em like butter!
- Tears of Joy: Dr. Viper actually cries thinking about how beautiful "Megaswamp City" will be.
- Visionary Villain: Whereas previously Dr. Viper just wanted to steal a chemical for no readily apparent reason, here he has an actual Evil Plan to turn the city into a giant swamp ("Ruled my me! Dr. Viper's Megassswamp City!").
- Unexplained Recovery: We aren't told how Viper survived blowing himself up at the end of his previous appearance.
- You Have Failed Me: After the Rover Plantimal that had been guarding Callie lets her get away, Viper smacks it into the window with his tail, cracking the glass. It fared even worse in the script, where it smashed through the glass, fell 300 stories and splattered all over Feral's car.
