List of Sgt. Frog episodes (season 1)

Sergeant Keroro is a frog-like alien from the planet Keron sent to invade planet Earth (or Pekopon, as his race calls it). He is instead kept as a pet and forced to do chores for the Hinata family, which consists of paranormal maniac Fuyuki, his ill-tempered older sister Natsumi, and their manga-editing mother Aki. Keroro is given his own room in the basement of the Hinata family house, which he refurnishes and uses as a base, not realizing that the room is haunted by a ghost.
In a prequel to the first segment, the Hinata family first discovers and captures Sgt. Keroro while he is scouting inside their house. Fuyuki takes the Keroball (Keroro's weapon) and fiddles around with it, accidentally sending a signal to the Keronian invasion fleet alerting them of Keroro's capture. The fleet abandons Keroro instead of rescuing him, leaving him to perform chores around the Hinata family household.

Keroro goes to Fuyuki's school in search of the other members of his platoon. Meanwhile, Fuyuki is stalked by Momoka, a girl who had come across Private Tamama, one of Keroro's platoon members. Momoka tries to confess her feelings for Fuyuki, but is interrupted when Tamama farts while hidden inside her schoolbag. Momoka angrily attacks Tamama, but Keroro arrives and saves her before the seemingly helpless Tamama snaps and counterattacks with his laser breath.
Momoka attends a meeting for Fuyuki's paranormal club at his house in an attempt to become closer to him, but is frequently interrupted by Keroro and Tamama's antics. Meanwhile, Keroro becomes jealous of Tamama when he discovers that his subordinate has been living a very pampered life at Momoka's mansion.

Keroro feels trapped inside the Hinatas' house and misses being outdoors. Tamama and Fuyuki help him think of ways he can leave the house without drawing too much attention, given that he is an alien. Keroro eventually discovers that the badge on his helmet allows him to temporarily turn invisible.
Natsumi suspects that Keroro will use his invisibility device to go out and cause trouble, so she convinces her family to install hidden cameras throughout the house to spy on him. Later, Natsumi accuses Keroro of spying on the family when she discovers a pair of binoculars outside, but the Hinatas survey the security footage to find that Keroro has done nothing out of the ordinary. The true culprit is later revealed to be Giroro, another member of Keroro's platoon.

Giroro is disgusted by Keroro and Tamama's lack of progress in the invasion, and decides to set traps for the Hinatas using all the information he had gathered on them. He immobilizes both Keroro and Fuyuki, but Natsumi easily overcomes the traps with her brute strength and knocks out Giroro.
Giroro suspects that the reason behind Keroro's lost interest in the Pekoponian invasion comes from a difference in humidity between Earth and Keron. He and Tamama install humidifiers in Keroro's room, which drastically increases his intelligence and strength, but the room becomes overly humid when it begins to rain, causing Keroro to go berserk. The humidity attracts a Nyororo, a natural enemy of the Keronians, which feeds on all the moisture Keroro had absorbed and returns him to normal.

Momoka invites Fuyuki to her private island resort for spring break so she can steal her first kiss from Fuyuki. However, Natsumi, Aki, and the Keronians come along and thwart her plans. She ultimately tries to pretend that she is drowning so that Fuyuki can save her and give her CPR, but Fuyuki reveals that he doesn't know how to swim. Momoka nearly drowns for real and is unknowingly resuscitated by an octopus-like creature brought by Keroro instead.
Hoping to be alone with Fuyuki, Momoka plans an island ghost hunt after everyone's dessert mysteriously disappears, not realizing that it had been eaten by the ghost that haunts Keroro's room.

Angol Mois falls over the Hinata's house and reveals that she not only knows Keroro but she's here to fulfill the prophecy of the Earth's destruction. She's already years late however. A battle between Keronians, humans and Mois starts for the control of the Lucifer Spear that would grant the destruction, conquer or safety of the planet.
Tamama jealous of the attention that Keroro gives to Mois puts her through an intensive training to scare her from ever wanting to be her partner. Tamama fails after seeing Mois's determination.

Keroro remembers yet again that he should be invading Pekopon so he convinces the Hinatas to do something outdoors while he and his platoon work in constructing a secret base.
Fuyuki and Momoka investigate the new secret base while the platoon thinks they are intruders.

Things are getting difficult for Keroro who realizes that the invasion needs someone intelligent so he orders to find the fourth frog Kululu. Meanwhile, Natsumi is approached by the popular Saburo who would like to hang out in her house for some reason. Fuyuki thinks it’s because Saburo is an agent hunting aliens, but in fact it’s because he found Kululu and it was time to reunite him with the Platoon.
Kululu's first invention in Pekopon is a ray that modifies the target's age and Aki is the first to try it. However, there is a time limit to change her back or she'll remain young again and Aki escaped to Fuyuki's school to pass the day.

Keroro gets a cavity for eating too many sweets and not brushing enough. However, Keronian cavities are caused by a microscopic alien race and must be exterminated from the inside. Kururu uses an invention to shrink Giroro and Tamama, and they go inside Keroro's mouth to beat the cavitians. Giroro and Tamama try but there are too many enemies for the two of them.

The Platoon gets notice that an alien crew of a reality TV show will arrive in Earth and they are ordered to help them with the show in whatever they need even if that includes getting really weird shots for them.

Space idol Sumomo arrives at the Hinata's house to offer a private concert for the troops in Pekopon. This is actually a lie. In fact, she just wanted to rest from all the attention she gets. In the end, after passing an afternoon as an unknown human, she realizes that she misses that attention and abandons Keroro leaving him with a huge debt from the concert planning.
Giroro finds a cat getting wet in the rain and decides to keep it. The next day he lost his belt and feels useless and clumsy. He even tries other things to replace his belt but nothing works. Turns out Kululu took it to show him that he indeed needed something to rely on and the cat found it for him.

Aliens all over Pekopon are being abducted and a new girl is transferred to Natsumi's group. Both things are related as the new girl Koyuki is a ninja protecting Earth who also found the last frog, Zeroro. Koyuki informs him and tries to reunite them but Zeroro refuses, revealing to his old friends that he changed his name to Dororo and will now protect Pekopon rather than invade it.
Dororo and Koyuki are taken prisoner by a member of the Vipers, natural enemies of the Keronians. The platoon goes to the rescue only to fail miserably for the lack of a fifth member. Keroro comes clean about breaking Dororo's music box a long time ago prompting Dororo to forgive him and help the platoon defeat Viper. At the end, Dororo realizes how painful was to remember his box and refuses to join them again.

Keroro works hard to come up with a plan to invade Pekopon but Dororo keeps refusing all of them for not being ecologically friendly. He wants to plant flowers to help peace flourish and an idea comes to Keroro that would satisfy everyone in the platoon.

After a freak accident involving Tamama's training machine, Momoka's two different personalities split up. The bad Momoka escapes the mansion looking for Fuyuki.
Bad Momoka ends up taking over the leadership of Keroro's platoon and Kululu shows her a destructive missile but stops at the last second. Good Momoka realizes that she needs her bad side back and only synchronized swimming will combine them back.

Dororo, Saburo and Tamama find Mois beating up people and head to the Hinata's house to investigate. Kululu shows all of them a video of Mois' activities which was supposed to be secret and a gift to her father. Mois walks on them and runs out of the house. The group runs after her to catch them attacking Natsumi's friends. Natsumi tries to stop her but Mois fights back. Then another Mois walks into the scene.
Mois explains that she took the appearance of that girl when she first landed in Earth. The Platoon decides to help the girl and discovers the reason behind her violence. Mois is moved and decides to destroy the Earth so she won't suffer anymore but stops at her request.

Keroro plans a trip to the school pool to test how good swimsuits actually stand against a Keronians. Once there Keroro challenges Natsumi to a swimming race which she losses.
Keroro and Tamama laugh at what Pekoponians think is scary so Natsumi challenge them back to a scary story telling competition of Humans against Keronians, with Giroro as the forced referee.

Keroro and Natsumi want to go to the beach but Aki can't go, so the only way Kululu thinks of is to zap Natsumi with the age modifying ray. Keroro then reveals that the reason why they had to go there is a comedy stand contest which prize is a mountain of fake but very rare Gundam knock off models and he wants Mois and Natsumi to win them. Natsumi refuses but Saburo appears and talks that he would like the models too.

Natsumi, Fuyuki, Koyuki and Mois go to a festival in which they find the Platoon scamming people. Keroro challenges Natsumi to a turtle fishing challenge to either leave the festival or keep her prisoner. Natsumi wins but Keroro has a plan B that involves the festival's fireworks.
Keroro discovers the persuasive powers of the radio and decides to host a show that would brainwash humans to hand over the planet. All goes well until they lie about having the space idol Sumomo and Giroro was not able to recreate her voice.

Keroro decides to start the Peokoponian invasion by conquering the sea and the Hinatas tag along. Fuyuki meets a girl and both clean the beach until Keroro calls him to dive to the deeps of the sea to help him with a school research.
Keroro and the Platoon continue to conquer the sea. They go to the deepest part where Fuyuki offers to go himself. The submarine is attacked by the Nantoma, a race that inhabits the bottom of the sea. The Platoon flees but Fuyuki is abandoned and they can't go back for him. Luckily he's saved by the girl he met.

A power failure in the middle of the summer leaves everyone heat stroked. Koyuki teaches Natsumi ways in which she can stay fresh without electricity.
The Hinatas visit Grandma in her house at the mountain and the Platoon tag along. Giroro feels the call of nature but falls off a cliff, Tamama finds someone with who to train and ends up injured and Keroro ends lost in the woods with a dog. The three of them are saved by a strange woman that rings a bell.

Tamama is appointed as the new leader of the platoon by headquarters. Quickly enough the power goes to his head, destroys all of Keroro's Gundam models and throws him into a pit.

Keroro sneaks into Fuyuki's room to take the Keroball and clones himself by accident. The number of Keroros keeps growing until the house is full of clones all of them as useless as the original.

Space Detective Kogoro and his sister Lavie land in Pekopon and confuse Natsumi with random comments. They follow Natsumi to the Hinata's house looking for aliens that threaten the peace of Pekopon. The Platoon and the detective fight but only Keroro wants to fight. At the end the fight was staged because Keroro and Kogoro were friends since childhood.
Kogoro decides to stay in Earth but it's hard for him to find a job because of his weird actions and speeches. Kululu finds him an audition in a children's program and is actually doing good until Keroro and Tamama feel jealous and jump into the show too.

Momoka refuses to visit her father Baio Nishizawa in Scotland so he decides he'll bring her by force with his army, the best army on Earth. Keroro wants to film the platoon taking down the Nishizawa's army so headquarters would think he is competent.

It's sport week and as always Fuyuki is not very optimistic of it. Natsumi plans to run the three leg race with Aki if she came make it in time to participate. Keroro decides to do whatever it takes to help Natsumi so she will own him a favor by sabotageing the events before the race.

Keroro gets a message from his father, telling him he is going to visit. To get the place prepared, he turns all of his friends into slaves.
The platoon creates a plan to make their own hot spring by drilling to find water. However, they get disastrous results.

Keroro and his friends have a regular snowball fight, but soon go to extreme mesures.
Kululu is tired of being the most unpopular character in the show, so he decides to play some nasty tricks.

Because of her popularity, Natsumi is forced to do a horror version of Peter Pan with Koyuki. After training with Keroro and a few other aliens, Natsumi is ready to take on the part of Wendy. Seeing Saburo in the audience, she gets too lovesick and makes a fool out of herself. It's up to Keroro to save the show!
A news group catches Keroro in person and want to put him in their next article. However, Keroro has other plans for the group.

Private Taruru lands on Pekopon, and thinks Tamama is the sarge, due to some lies on Twitter. He makes hurtful jokes at all of Tamama's friends, and they all soon get revenge.
Momoka gets a complete makeover to make Fuyuki like her more. But it doesn't exactly work as planned.

Keroro rides his new space bike everywhere until it runs out of fuel, and he gets lost in a forest.

Keroro decides to attempt to grow his army by turning animals into soldiers to join the platoon. Things do not go as planned, as usual.
The cat outside gets a hold of the gun that turns animals into humans in oder to say something. (Gun previously mentioned in the last episode)

Fuyuki wins 4 tickets to a spa (from a game rigged by Momoka, hoping he would take her). However, Koyuki is invited instead. Meanwhile Keroro is determined to solve a rubix cube given to him by Natsumi in order to go.
Keroro accidentally breaks Natsumi's favorite coffee mug, so he runs away, but later meets Fuyuki, who is on his way to school for a big math test. Keroro and Fuyuki then walk across a lane, in which Fuyuki sees some familiar places he went to within that lane when he was little kid.

After Fuyuki refuses to take him to the toy store, Keroro decides to get his revenge by putting them into a simulator that produces ice cold temperatures. However his plan backfires when Fuyuki and Natsumi are having fun, rather than suffering from the cold.
After Tamama tells her what happened in the previous episode, Momoka decides to take everyone on a trip to her ski resort

When Keroro finds himself in debt, he decides to open a ninja training school, with Dororo as the teacher. Since nobody shows up, Keroro decides to have Dororo teach the platoon the ways of the ninja, however they struggle to pay attention.
When Natsumi seeks to get revenge on Keroro, she and Fuyuki find themselves in Keroro's latest plan: Triassic Garden.

Sumomo and Keroro use hidden cameras to get a laugh out of Giroro's feelings for Hinata, but their plan backfires when a powered-up Natsumi goes on a rampage.

Christmas time is here, and Keroro plans on using this time to finally conquer the world. However, Keroro is worried that Santa Clause will be first to conquer the planet.
Christmas has come and gone, and now Keroro plans on starting the new year with the greatest house cleaning operation ever.

Keroro decides to welcome in the new year with many games, most of which involve using Giroro as a test dummy.
The frogs get mail from children from their home planet. When a letter comes requesting Keroro's assignments to be handed in, the platoon has to keep a constant watch on Keroro until he finishes them.

Keroro and Natsumi get into a heated debate over a very small problem. In order to solve the debate, Keroro and Natsumi play a game where they themselves are the pieces.
Dororo seeks help in order to get attention from the people around him.

Keroro enters the platoon into the world cup, hoping to gain control of Pekopon. Everything goes well until Keroro kicks the ball into his own goal.
Tamama meets a young soccer player who isn't really good, so Tamama decides to become his teacher.

After reading a fairy tale about colorful ogres, Keroro hatches a plan to acquire the ultimate power of the Hinata house.

When a case of spring fever sweeps through the Hinata house, Keroro hatches a plan to take over the world with a wave of laziness.

Kululu inspires his fellow invaders when he mysteriously starts helping out around the Hinata house. Meanwhile, Momoka will stop at nothing to make a virtual love connection with Fuyuki.

Natsumi is stricken by a deadly fever during the Keroro Platoon's latest invasion attempt. Giroro blasts off on a mission to find medicine, but first he must defeat a three-headed space monster.