Ash and co are now taking a break in a city harbor's park area on their way back to Petalburg City. As they have a small picnic, Ash comments on how he can't wait to have his next gym battle. Max remarks that his father will be hard to beat, but Ash says he knows this already. May remarks on how much she can't wait to see home again, and the siblings begin to discuss their family. Max seems excited and wants his mom to cook hamburgers.

At this, May goes in for one of the sandwiches, but it becomes apparent that something made off with hers. Max watches as a Gulpin slides by and eats everyone else's sandwiches too; bowls and all. They all then watch it horror as it swallows and spits up the bowl. Ash scans this new Pokemon with the Pokedex to find out it has a large appetite. The group begins to discuss it and May remarks on how funny it looks.

Suddenly, an actual state-of-emergency alarm blares throughout the entire city from a loudspeaker. Nurse Joy is heard from the speaker while the siren still blares. She warns pedestrians that Gulpin are massing on the city and a state of emergency has been issued. Ash and co are shocked by this. The group heads into the streets of the city to find them completely evacuated. Max and May wonder how they could evacuate a city just because of a Pokemon infestation.

Suddenly, a woman's scream is heard nearby. The group rushes to the scene to find a bakery. Inside is a scared woman leaning against the wall. Ash asks her what's going on and she points nervously at the bread counter. A group of Gulpin has massed themselves onto it and is eating everything. Ash tells Pikachu to give them a thunderbolt, but Pikachu is immediately body slammed by every single one. Ash rushes to the pile of Gulpin and fishes Pikachu out only to find it paralyzed.

May then freaks out as a large amount of Gulpin begin to pour in from the ceiling vents. The group is soon being covered by the vast amounts pouring into the room. Brock then hears a whistle and immediately recognizes it as Officer Jenny's. He goes lovey-dovey at the sound, exclaiming that his heroine has come to whisk him away. Suddenly, the Gulpin pile over him and he's lost to the mass of Pokemon. Officer Jenny arrives right on cue and has her Tangela use vine whip to grab the group and pull them out of the Gulpin mass.

The Gulpin group then exits the bakery and slide down the street. Ash and co thank Jenny for saving them as they recover from the horrifying experience. Jenny wonders why the group didn't heed the warning given by the loudspeaker, but Max just comments that they are new to the area and didn't know. The baker also says she was partly at fault. Jenny then suggests that they head to the Pokemon Center to continue the conversation.

There, the local Nurse Joy displays a map of the city that also is tracking the movement of the Gulpin group. She explains that they have finished the current street and are moving to the next. Brock is turned on by her determination and begins to get all infatuated again. Max then cuts in annoyed with his comments. Ash and co then ask Joy where she got all of her equipment, and she explains that the town has grown so tired of the Gulpin showing up that they hired a scientist named Shakuji, who studies Gulpin, to rid them of their problem.

Ash and co are confused when suddenly a scientist that resembles Santa Claus appears next to them. Nurse Joy explains that Shakuji is a very famous expert on Gulpin behavior. Shakuji then asks where the Gulpin are as of now, and Jenny brings up a visual. The Gulpin are currently split between the grocery store and the desert bakery. Shakuji then leads Ash and co to the map and shows them how close the Gulpin mass is at reaching the Pokemon Center. Apparently they are using the sewer system to travel faster. Everyone begins to worry.

An alarm suddenly goes off and everyone watches as the Gulpin begin to make their way towards the center of the city (where the Pokecenter is). Jenny sounds the emergency alarm throughout the city and tells the group that they have to stop the advancing feasters. Jenny and the others set up a blockade with a large truck at the entrance of a nearby bridge. There, they all prepare for the Gulpin to show up. Jenny asks if Ash and co are ready and they say they are.

The Gulpin swarm begins to appear on the other side of the bridge. Shakuji sees this from inside the truck and pushes a lever up. This opens the back of the truck and a large missile appears. It locks onto the Gulpin swarm and Shakuji activates it. The missile launches high, and then begins to fall towards the Gulpin group. It then opens up and a very large Pokeblock dispenser emerges. It lands in front of the Gulpin who begin to inspect it.

Shakuji then exits the truck as Ash and co wonder what's going on. Shakuji explains that no Pokemon can resist Pokeblocks, and he plans to use the contraption to lure the Gulpin away. The Gulpin begin to mass on the dispenser when a helicopter blade activates on the top and makes it lift off the ground. The Gulpin currently on it are thrown off and they all watch as their food begins to move away. It heads off in the other direction and the Gulpin give chase. Brock can't believe it's working and Shakuji laughs, exclaiming that it worked like a charm.

Suddenly, the Pokeblock dispense is grabbed from above by a metal hand. Team Rocket laughs from their balloon and Shakuji demands they release the dispenser. Team Rocket refuses and says their motto. Shakuji is confused and Ash explains that Team Rocket is no good. James then corrects him, exclaiming that they have to be decent to be able to steal the dispenser. May then demands they give it back so they can lead the Gulpin away, but Jessie says the Gulpin will just have to come get it themselves. Suddenly, the Gulpin swarm begins to launch sludge bombs at the balloon.

The balloon is soon covered in sludge and it crashes onto the bridge. Team Rocket emerges complaining and begins to yell at the Gulpin. The Gulpin then turn purple as they begin to stockpile. Shakuji is impressed by this and says a stock pile always is followed by a spit up. Right on cue, the Gulpin launch their spit ups, smashing into Team Rocket and sending them blasting off. As they are sent flying, the Pokeblock dispenser falls from Jessie's hands and Brock manages to catch it, but smashes himself in the process.

Shakuji thanks Brock and then begins to say how impressed he is by the Gulpin groups' combination of attacks. Max then cuts in exclaiming that the Gulpin are heading this way! Shakuji looks to see Brock freak out as the Gulpin rush to him. Jenny cuts in releasing Tangela, Meganium, and Parasect to protect Brock. She has Tangela use vine whip, Meganium use razor leaf, and Parasect use stun spore to slow the Gulpin swarm down. May is impressed by the grass types but Max exclaims that Gulpin is a poison type and isn't affected much by grass attacks.

Ash then decides to join the fight by releasing Treecko. It emerges placing the twig in its mouth and stares the Gulpin down. The group releases sludge bombs, but Treecko dodges and uses bullet seed. Before anymore attacks are launched, however, Shakuji activates the Pokeblock dispenser. Brock freaks out as the flame bursts from its bottom and causes the dispenser to jet off down the river. The Gulpin swarm makes a dive and begins to swim after it. Ash and co cheer as they leave, but Jenny reminds them that the swarm will be back and they should prepare for it.

Meanwhile, Team Rocket walk along the river depressed from their previous blast off. Wobbuffet then notices something and the group looks to see an empty Pokeblock dispenser and the Gulpin swarm leaving the scene. They realize how valuable the swarm could be in leading them to food, so Jessie suggests they try following them. Everyone seems to like the idea, so they begin to head off.

Night falls on the city and the alarm sounds out once again as Jenny alerts everyone about the Gulpin swarm that is coming back. Ash and co watch the map and realize that the swarm is heading straight to the Pokecenter by the sewer system. They all wonder what to do next. In the sewers, the Gulpin swarm slides on as Team Rocket follows. The thought of food is now more on their minds than it is on the Gulpin'.

Jenny then tells Joy to activate the shutters. Joy does so, and the two sewer entrances to the Pokecenter are shut off. The Gulpin swarm takes the remaining path, but Joy knows this only bought them some time. Shakuji says it isn't going to work as the Gulpin never stop searching to feed their appetite. He says they don't have much time before they find a way into the Center, most likely taking the streets here. Jenny volunteers to go stop them. Ash decides to help, and they all head off.

The Gulpin emerge from the sewer and into the streets. They then begin to make their way towards the center by ground level. Ash and co along with Jenny suddenly block their path. Ash sends in Pikachu and Jenny releases her three Pokemon. The Pokemon all use their signature moves, blowing some of the Gulpin back. They keep attacking, but nothing seems to stop the hungry Pokemons' advance. The Gulpin are now heading straight towards the group, but suddenly Shakuji comes from an alley in his truck blocking the Gulpins' path. He activates a switch causing a large cannon and two satellites to emerge from the truck. Ash wonders what he's planning and stares in awe.

Shakuji activates the satellites and purple energy sucks the Gulpin up. Ash and co wonder where they are disappearing to and Shakuji activates another switch. This causes the cannon to launch the sucked up Gulpin one by one out of the city. Ash and co are in awe at this contraption, and Shakuji continues to get rid of the group in this manner. Ash and co then wonder how it works and Shakuji explains it to them. He says it works much like a Pokeball in sucking up the Gulpin. It then registers them into his truck, and finally launches them back out harmlessly out of the city.

After some time, the group notices that only one Gulpin remains. Shakuji goes to suck it up, but his truck suddenly shuts down. Shakuji says he must have used too much power and begins to fiddle with the switches. Ash then decides to have Treecko get rid of the lone Gulpin. He calls it out and it launches a bullet seed, but Gulpin uses sludge bomb to counter it. Shakuji begins to fiddle with his machine and it finally comes back online. Ash tells Treecko to pound Gulpin. It connects with the Pokemon right when the satellites launch catching them both in the beam! Everyone watches in horror as both Pokemon are sucked up and registered at once into the machine.

Gulpin then takes this time to stockpile/spit up, overriding the machine and causing an explosion. Ash pounds on the truck demanding the release of his Pokemon as May tries to pull him back. Shakuji fiddles with some buttons again, and ends up causing an explosion. When the dust clears, Joy makes sure everyone is all right. Shakuji then notices Treecko and Gulpin being lifted by some purple glow in the distance.

As Ash and co watch, the two Pokemon grow to Godzilla-like proportions. They tower over the buildings as Ash and co begin to freak out. May makes a dumb remark that has her brother sigh. Brock then wonders how this happened and Shakuji says the spit up must have overridden the system and caused a side effect. Gulzilla then begins to move towards the Pokemon Center, smashing into buildings as it goes.

Ash rushes up to Treezilla and tells it to stop Gulzilla from making it to the center. Treezilla nods and leaps over Gulzilla. It lands in front of the Pokemon and glares at it. What follows is right out of a Godzilla flick. Jenny urges the citizens to flee as they all run screaming. Treezilla fights Gulzilla in the background. The Pokemon lifts Gulzilla up and smashes it into a building. Gulzilla then releases a sludge bomb making a large explosion. Max is shocked and May is worried about Treecko. Shakuji just wants to know how to reverse this effect.

Treezilla smashes into the street and Ash is forced to run to avoid some debris. He then grabs a random loudspeaker and tells Treezilla to get Gulzilla into the river. Treezilla nods and grabs Gulzilla. It then spins around and launches Gulzilla as it begins to stockpile. Meanwhile, Team Rocket exits the Pokecenter fleeing with bags of food. They are happy with their theft when Gulzilla suddenly floats by. It launches the spit up at that moment and ends up hitting Team Rocket by accident. The group drops their hard earned food as they blast off.

Gulzilla then smashes into the water as Treezilla follows in after it. Gulzilla surfaces and smashes into Treezilla, sending it flying into a building. An alarm sounds as Ash and co wonder what to do. Max points out that Treecko seems to be weakening. Gulzilla then prepares and launches a stockpile/spit up combo, but Treezilla leaps out of the way. The attack goes by and Treezilla suddenly begins to glow and shrink. Apparently it ran out of energy and caused the effects to wear off.

Treecko returns to normal size right by Ash and he rushes to see if it's all right. It's breathing heavily and Joy suggests he have it rest in its Pokeball. Ash agrees and recalls it. Meanwhile, Gulzilla begins to head back into the city and everyone panics. Shakuji is at a loss of what to do, and Ash pulls out a Pokeball to have a different member of his team go up against Gulzilla. May then gets an idea and tells Shakuji that Gulzilla is still a normal Pokemon, and he should be able to catch it with a Pokeball now that Treecko weakened it.

Shakuji thinks she's right and he decides to try. He throws a Pokeball and Gulzilla is sucked inside. However, the ball doesn't even hit the ground before the Pokemon escapes. Shakuji doesn't know what to do now, but Joy suddenly approaches him. She hands him a heavy ball and he begins to get confident. Brock explains that Gulzilla is probably so heavy now that the heavy ball will have no chance of letting it escape. Shakuji takes the heavy ball and throws it at Gulzilla. After many shakes, the ball stops and Gulzilla is subdued.

Everyone cheers and the sun comes up as Shakuji picks up the ball. Brock wonders if the effects wore off now that it's caught, and Shakuji says he they must have. He then lets out his new Pokemon to find out it's still colossus. Everyone freaks out (especially Jenny). She tells Shakuji to recall it before this whole mess happens again. He fiddles with the ball before managing to recall it.

Ash wonders what Shakuji plans to do now and he explains that it either needs more time for the effects to wear off, or he'll have to work on a way to reverse the effects. He says he'll figure it out eventually, and they shouldn't worry. The episode then ends with the group looking out at the sunrise.

Thanks To GoldenNoctowl77 For Writing this for us