Dedede creates an amusement park for all the Cappies, but when Kirby and friends get lost in the castle, they soon learn that this amusement park is really a trap.
Spoiler alert: The following section contains plot-specific details.(Skip Section)
It all starts out when King Dedede and Escargoon announce that they are going to have an amusement park over at Castle Dedede. The Cappies are ecstatic and comes to the party. Even Kirby comes, but Tiff and Tuff suspect something is going on. Fololo and Falala say it's too public for King Dedede to trap Kirby, so they all have fun. Once Tiff, Tuff, Kirby, Iroo, Spikehead, and Honey got on a ride, they were flung off and sent onto a roller coaster. They fell off after going a few yards on the roller coaster. They fell in a hole and finally realize it was a trap when Dedede and Escargoon appear on a screen telling them they were about to test their scariest ride, the Crushing Caverns. They refuse, but Kirby finds a watermelon on the seat of the roller coaster and goes after it; a decoy. This forces everyone to go on the ride.
Meanwhile, Dedede and Escargoon are watching the kids on cameras placed all around the caverns, but the cameras were disabled by Sword Knight and Blade Knight, later found in the cave. Once Tiff and friends are in a large room, giant Dedede statues were to attack them until Meta Knight intervenes. Meta Knight, Sword Knight, and Blade Knight help Kirby and his friends escape to tell the cappies the park is a trap while Meta Knight and his men destroy all Dedede statues, leaving Dedede and Escargoon confused. Dedede then decides to order a monster.
King Dedede orders Walky from Nightmare Enterprises. Customer Service suggests (somewhat jokingly) to hold a Karaoke contest with it, the grand prize being Kirby's favorite food, watermelons. Kirby would stand on the "stage" (actually the NME Teleporter) and be sent to NME to be destroyed by the overwhelming numbers of monsters there. After several attempts to get on to the "stage" and sing (his attempts denied by Mayor Len Blustergas, Chef Kawasaki, and Sir Ebrum, to name a few), Kirby inhaled Walky and became Mike Kirby. Nobody knowing what would happen (not even Meta-Knight), Kirby then proceeded to sing "Kihon wa Maru" badly. Customer Service managed to upload him to NME, however, Kirby's bad singing destroyed all the monsters, and the singing was far too much for Customer Service to handle, so he was sent back to Dream Land. As Kirby reappeared in Dedede's castle, the castle began to crack and fall apart. The castle floor cracked open, and Tiff, Meta Knight, and everyone else fell through the floor. Meta Knight, realizing Kirby's new ability, said, "Now that we have experienced this ability, the Microphone Ability may be Kirby's most dangerous attack of all!" By the time Kirby had finished singing, he had destroyed Castle Dedede. In the end, Kirby wanted to sing again, but Walky ran away. Likely because he didn't want to be inhaled again, or simply because Kirby's singing was awful. Moments later, King Dedede and Escargoon run from Kirby in a panic the same way Walky did.
In the dub, when King Dedede is asked to pay his bill, Dedede claims he sent him a check in the mail. In the Japanese version, Dedede says he's a customer, so he's god.
The scene in which Kirby, Tuff, Fololo, and Falala stop at a plush dispenser and get yelled at by Tiff was removed in the dub for unknown reasons.
Every time Kirby sees the grand price of the karaoke contest, which is a lifetime supply of watermelons, he cries out "Suika!", which means watermelons in the Japanese. Same goes when King Dedede reminds Kirby about the melons. This was replaced with "poyo" in the dub.
In the Japanese version, Escargoon was starting to sing "Hound Dog" by Elvis Presley while holding onto Walky. In the 4Kids dub, he did a brief parody of it based on Kirby and his ability to swallow.
Customer Service swapped his usual pair of sunglasses for a blue-lensed, red-framed pair for the Karaoke Event. He changed back to his original black-framed, orange-lensed pair in future episodes.
Kirby sings "Kihon wa Maru" in the Japanese version. The sounds are so bad, every note Kirby sings warps the wormhole connecting Dedede's throne room to Nightmare's Fortress.
A different song is used in the English 4Kids dub while Mike Kirby is singing. Most of the original sound effects were retained as well as some newly added sound effects created by 4Kids. Ironically, Kirby still sings "Kihon wa Maru," causing the new music to contribute to how horrible Kirby's singing is (since the new music isn't the same tune as the vocals).
In the scene where Kirby, Tiff, Tuff, Fololo, Falala, Honey, Spikehead, and Iro go on a boat ride, Fololo and Falala are in the second row of the boat. In the next scene, however, they are in the first row with Kirby and Tuff and the back row is empty, even though it was occupied by Honey and Spikehead.