Brady and Boomer are just to ordinary twins. Or, so they thought. They soon learn that thier parents were king and queen of a small island and they are next in line to rule. But,thier distant cousin is planning to stop them from being kings. Part 2 The twins must save thier island from an errupting Volcano that they awakened. To do this they must cross into the dark side of the island and find a replacement rudy which is a task imposible to do. Lanny tells the villagers that Brady and Boomer are dead so he can become the next king.
Boomer and Brady meet an odd creature in the woods named Ogie (Doug Brochu). But Brady is jelous of the Ogie and is mean to him. Brady fills a void by being Lanny's friend, but Lanny's plot is to kill him. But when Boomer is invited to a feast, he isn't going to a dinner; he is dinner—or so it seems.
The kings must perform for the islanders at the Annual Harvest Festival, and Boomer can't wait to show off his singing skills. Brady knows Boomer has a horrible voice, but doesn't have the heart to tell him. When Brady's plan to protect his brother from humiliation backfires, Boomer discovers Brady is a terrific singer and arranges for Brady to sing to the kingdom.
Feeling homesick, Boomer and Brady call Aunt Nancy and Uncle Bill to check in, but accidentally end up scaring them with their tales of Tarantula people, quick sand and giant bugs. While Aunt Nancy and Uncle Bill rush to the island to bring the twins back to Chicago, Brady is accidently stung by a dangerous Waka Waka bug. With the help of Mason and Mikayla, the kings must hide Brady's strange side effects including pumpkin head and amnesia in order to prove that the island is safe enough for the kings to stay and rule. Meanwhile, Mason has a date with a girl named Stewy.
Boomer and Brady discover Vault 14, a secret vault which protects Kinkow's most mysterious and powerful artifacts. They find the Duplicatus Plantus, a plant that copies anything it touches and make clone of themselves. The clones fill in for Brady and Boomer so that they can go surfing, However, clones want to replace Brady and Boomer forever.
It's the kings' birthday and for their royal present, they each get one wish that will come true. Right before blowing out the candles, Boomer learns that Brady has been bragging to the entire island that he is the older twin. Boomer uses his wish to find out the truth about who was born first, while Brady's wish is that Mikayla compliments him all day. Boomer travels to the center of Mt. Spew to meet with the volcano's Oracle and learn who is the older king, but the younger brother will no longer be co-king if it is known who the older brother is. So Brady, Mikayla, and Mason chase after Boomer.
While trying to prove that they are the Kings of Legend, Boomer and Brady accidentally bring Zadoc, an ancient evil statue, to life, consequently putting the entire island in extreme danger. The twins cede the throne to Lanny for the better of Kinkow and depart on a balloon voyage back to Chicago for good, until the balloon catches a wind and sends them plummeting straight to the Dark Side of the island.
Brady finally musters up the courage to ask Mikalya out, by using a note Lanny wrote for him, but he reconsiders and decides to ask her in person; when Brady attempts to retrieve the note, Mikayla mistakenly assumes the note is from Boomer, and he learns that before dating a girl in Kinkow you must be hunted down by her father. During the night while Boomer is getting hunted, Brady tells Mason that he is the one who wants to go out with Mikayla. Mason starts hunting Brady. Brady spits an egg at Mason, knocking him out. In the morning they go back to the Kingdom and Brady asks Mikayla out but she says no, because he humiliated Mason in front of the people of Kinkow.
When the Kings' over-the-top spending causes a monetary crisis on Kinkow, Lanny has the islanders pay mandatory donations to the kings. Buying time until they find a better solution to fix the crisis, Brady and Boomer disguise themselves as bandits Sirocco and Sirocco Taco, stealing the kingdom's donations and returning the money to the public. With criminals on the loose, the Kinkowians start to get angry and the kings must find a way to restore the island's fortune, capture the criminals and win back their kingdom's support.
Boomer and Brady are flattered when a pair of cute Queens from the neighboring island compliment their latest ridiculous invention and ask them to be the Kings of Sununu. However, the Kings soon realize that the Queens and their kingdom are victims of a dumb-curse. In order to help cure the entire island of stupidity, Boomer and Brady must solve the Statue's riddle. When Brady gets the riddle wrong so the girls could still admire him and Boomer, the Statue puts the dumb-curse on King Brady, forcing Boomer to get help from Mason, Mikayla, and Lanny to solve the riddle by sunset or else they will be dumb-cursed.
Mason's brother Jason visits, but Mason isn't so welcoming due to an incident when they were kids. When the kings make Jason head guard, Mason quits and drowns his sorrows in eating. But when the Tarantula people try to roast Boomer alive, Jason cowardly runs off and it's up to Brady to convince Mason and his pregnant self to come back and save Boomer. When Mason arrives, he and King Brady are captured by tarantula people. The Jason's water skuter falls on two tarantula persons, and Jason falls on other two.
Boomer opens the teen hotspot of his dreams and hires Brady as his assistant. When Boomer fires him, Brady spitefully opens his own club across the way inside a crypt upon being guided there by Lanny. When Brady performs a new song for the crowd with the lyrics having been provided by Lanny, the club is overrun by zombies that have been awakened by the song. Now it's up to Boomer to put his differences aside and rescue his brother.
When Mikayla's ex-boyfriend Lucas (a pirate who broke her heart) refuses to participate in the official Kinkowian Dumping Ritual, the kings track him down and discover that Lucas looks just like Boomer. To help out his quest to finally date Mikayla, Brady makes Boomer impersonate Lucas and pretend to go through the official ceremony, but the plan backfires.
The kings want to introduce their subjects to their favorite holiday traditions of Christmas. They enlist the help of the islands giant elves to make the toys. Thanks to bad advice from Lanny, the elves revolt and the kings believe that their Super Christmas is gone only to be rescued by the jolly old elf himself.
Mikayla finally has enough of Brady's constant flirting and tells him that their friendship is at an end and it would be only professional from that point on. Later she and Boomer seem to be getting closer as their share a hobby of Kinkowian poetry slams. Brady in a fit of jealousy, outlaws the poetry trying to end the new friendship. And the fight is on.
When King Brady misses his favorite sneakers it's King Boomer that blames a monster that nobody has seen except him that he calls Mr Boogey. Nobody believes him, thinking he got rid of the stinky shoes. However Mason has been keeping a secret about the creature for years. After Mason is captured by the creature it's up to Boomer to prove Mr Boogey is real.
Lanny lures the kings into the domain of the Nanju Warrior tribe, which are beautiful young women who have mastered the areas magnetic fields and appear to nearly fly. Unfortunately for Lanny the tribe has high respect for the Kings of Kinkow and it winds up that Brady goes on a date with one of the leaders, Sabrina who is Mikayla's rival from their fight school days. When Mikayla refuses to duel with her Sabrina kidnaps Brady and cages him high in the trees in a trap that is about to fall to his doom unless Mikayla fights. While the two girls battle on land, tree and air, Boomer rescues his brother.
The kings discover that they are about to be forever remembered by their Chicago high school class as having thrown the worst party ever. Against Mason's advice they bring the entire class to Kinkow for the best Beach Party ever. Lanny switches beach signs and the party heads for the hunting grounds of the giant Kinkow Sand Maggot who has its own ideas for party snacks.
The head chef quits when he is ordered by King Boomer and King Brady to prepare a steak cake when he was supposed to be making a very important meal for a giant ogre who is about to wake up from annual 10 year sleep, and when the ogre wakes up and demands food, the kings have to make a dish for him to save the island from his wraith.
When two moons appear, the kings meet the ghost of Malakai, the first king of Kinkow, who explains that an evil twin will destroy the island. After interrogating every twin on Kinkow, Boomer and Brady begin to turn on each other. Following Lanny's advice, the kings journey to the dark side to evil kings castle to sit on the evil throne and learn the truth. The prophecy comes true when the evil king is revealed, putting Brady under a spell and morphing him into evil Brady. With Mason and Mikayla in tow, Boomer heads to the dark side to save his brother and the island from sinking into the seas. Meanwhile, following a dream where she kissed Brady, Mikayla believes she may have a crush on him. Her friend Candace tells her that she does. Later when heading on with Boomer and Mason to save Brady from the evil king Kalakai, an evil Brady engages Boomer in a sword fight. Just before Brady can finish off Boomer, Mikayla gives him a long kiss, breaking him from Kalakai's spell. Together Brady and Boomer use their special rings to defeat Kalakai. Brady takes Mikayla's hand and asks what's next. Mikayla in turn tells Brady that the kiss was just to save him and it was for the love of her country, and walks away. It is still implied that Mikayla may still actually love Brady but just simply told him that the kiss wasn't about that. Brady, Boomer, and Mason follow Mikayla back to the castle where Brady claims that "she so loves me."
When Brady overhears Candace gossiping with Mikayla, Candace states that Mikayla said that she will never date him, since he is immature and will never grow up as long as he is the king of Kinkow, Brady leaves the island to go back to Chicago and vows to never come back until he can prove himself to be worthy of Mikayla. Boomer finds out about this and tries to follow Brady. But when a storm hits Kinkow sending people from the neighboring island of Mindu to them, it forces him to stay. They find the young king of Mindu has the Kinkow birthmark on his bellybutton which means he is also the king of Kinkow. It reveals that the boy is Brady and Boomer's long lost triplet brother, Boz.
Boomer teaches Boz about the Ten Bro-Mandments. However, a Tarantula Girl named Mary-Ann comes between them after she finds Brady's King Ring. Lanny tells Boomer that Boz is in the jungle, so Boomer goes after Boz, not realizing that Boz was up in the rafters. Boomer meets Mary-Ann in the jungle and she leads him to the Tarantula People and shows him Brady's King Ring. She throws it in the ditch. Boz saves Boomer from death & Boomer uses his secret ballet skills to defeat the Tarantula People. Boz's coronation then takes place.
When Boz defies Boomer's warnings and goes to the Dark Side, he finds a baby and brings it home only to discover the Tarantula People are threatening war because someone has stolen their baby prince. Boomer and Boz must learn to work together and return the feral, hissing, highly mobile baby to the Tarantula People before war breaks out.
When Boomer and Boz tarnish Mikayla’s first chance of beating Mason for "Guard of the Year", they feel guilty and secretly set out to help her win the coveted award by putting themselves in danger. When their attempt fails, they try to distract Mason and give Mikayla an edge by setting him up with a pretty girl who turns out to be his ex-girlfriend that wreaks havoc on Kinkow. In the end, Mikayla wins Guard of the Year.
Boomer, sick of Mikayla's awkwardness and overall lack of coolness, decides a summer vacation cruise with the rest of the island's teens could be just the ticket to make her more popular. But when Boomer unknowingly steers the ship into the Dark Side waters trying to impress some girls, the only teens Mikayla befriends are undercover amphibious creatures that have snuck aboard in search of live offerings for their swamp dwelling overlord, a massive bullfrog. When the summer vacation goes awry, the kings and the rest of the teens have to rely on Mikayla to save them.
Boz tries to prove to his ex-girlfriend that his life is better without her by putting on a big charade portraying an impossibly amazing life, complete with his own servant (Boomer), a magical troll that grants wishes (Lanny), and a pet Sasquatch (Mason). Unbeknownst to the kings, she doesn't actually care about Boz and is only there to take the riches he made up, including Boomer and Lanny.
When one of the Kings' stunts gets Mikayla suspended, the boys refuse to take responsibility. Mikayla calls them horrible bosses to herself, quits her job as their protector, and takes a job at a local fast food restaurant. When the Kings' attempts to get her back fail, they buy the restaurant and become her bosses all over again.
When Mason thinks Boomer's club is too rowdy, he takes over as head bouncer, but starts to keep the party out. In order to get Mason away from the club, the Kings lead him on a wild goose chase leaving the club wide open and vulnerable to a mythical human-like sponge creature named Damone (played by WWE's "The Miz") who absorbs everyone's confidence.
Boomer and Boz are each granted one wish on their birthday. Boomer wishes for the island to be danger-free for a date with his girlfriend Rebecca "Awesome" Dawson (who arrives on Kinkow for a visit). Boz wishes for him and Boomer to be closer, but gets more than he bargained for when they become magnetically attached. Things get worse when Lanny arranges for Boomer and Rebecca to have their date at Lightning Grove on the Dark Side of Kinkow.
After all that Boomer has taught Boz about living in the civilized world, Boz decides to address Boomer's lack of survival skills and forces him to go camping. Although Boomer is resistant at first, he has no choice but to become a fast learner and use his newfound skills when the camping trip goes awry, and he needs to help Boz fight for their lives against a jungle werewolf.
The Kings turn down the Goat Sisters Billie and Nannie (who wish to be their dates to the "Queen Uber Oogli Dance") and are then changed by a curse into ugly, unrecognizable versions of themselves. Now they must break it by dancing with the fairest girls in the village which is much easier said than done.
When Boz sets out to help Boomer make his childhood dream of becoming a professional athlete come true, Boomer believes he's a natural at the dangerous island sport of Thumb War. With a chance to become a pro thumb warrior, Boomer wagers the castle and loses, only to find he's been conned by a Dark Side crook.
When Boomer discovers that he and Boz do not have any brotherly memories like he and Brady do, he sets out to recreate a ski-trip from his childhood. But, when Boomer finds that the land he wants to build his resort on is occupied by Yetis, he removes them from the land and attempts to teach them how to be civilized.
Boomer, Boz, Mikayla, Mason, and Lanny watch Candace's show revealing the mysteries of Kinkow, causing Boz to have doubts about being Co-King. When a temple is discovered belonging to an ancient evil named Kaita the Bat Rider (whose mummy is in the possession of the Tarantula People), Candace is trapped inside and the entrance is sealed by a force field that only the Kings can get through.
Boomer goes to Chicago in an effort to convince Rebecca's father to let him see her after he forbids them to be together. Boz tags along and searches for a safe place to hide the Bat Medallion. Meanwhile, a menace from the past launches a surprise attack on the kings and it is revealed that Rebecca's father used to be part of the Tarantula tribe. As a result, he erases Rebecca's memory of her relationship with Boomer to keep her safe.
The Bat Medallion that Boz in Rebecca's apartment has dragged Rebecca to Kinkow. When Mikayla confiscates the Bat Medallion, Kutamungo captures her and the Bat Medallion in order to revive the Tarantula People's leader Kaita the Bat-Rider. The Kings fear of Kaita the Bat-Rider turns into revenge when they discover the evil Kaita is responsible for their father's death.