- Donkey Kong
- King K. Rool
After their last adventure, Princess Peach rewards Mario and Luigi with a trip to Kongland (as called in the Mushroom Kingdom). She and Starlow remain behind to take care of the kingdom as they set off, wishing them a good trip.
After landing in Kongland, they are suddenly attacked by reptile-like creatures, they defeat two of them, but then are surrounded by a crowd of them. Donkey Kong suddenly swoops in and saves Mario and Luigi.
Donkey Kong tries to explain, but as he doesn't speak English, he just draws pictures. Mario and Luigi interpret that Donkey Kong's enemy, King K. Rool, is attempting to steal an egg that grants ultimate power to the person who hatches it. They set off to stop King K. Rool.
They encounter a yellow fairy who was hurt badly by King K. Rool. Luigi helps her, and she takes a liking to him. She states her name is Merry, and Mario tells her the situation. She agrees to help them on their adventure.
Mario, Luigi, Merry, and DK learn from Cranky Kong that the egg is at the bottom of the ocean, deeming it impossible to reach. When Donkey Kong throws a fit, Cranky Kong says that he knows of an artifact called the Airstone that allows people to breath under water. He states that all five pieces are guarded by ancient monsters, who won't hand their pieces over easily.
The four gather all of the pieces after a tough search, and assemble the Airstone. They go under the sea, and find the egg. They are attacked by an undead giant blooper, and they defeat it.
When they are about to grab the egg, a crane comes down and snatches the egg. The source of the crane was King K. Rool's ship, who boasts about how he now has the egg. He starts sailing away, but Donkey Kong swims after the ship and stops it. The three and Merry fight their way through the ship, and get to the poopdeck. King K. Rool has already put the egg in an incubator, and is trying to hatch it. He turns around, and attacks the four with his canon device. He is defeated, and collapses. The egg starts hatching, with tentacles and a beak breaking out of it. Mario and Luigi are confused, while Donkey Kong is freaking out. He draws more pictures, and the two realize that the egg doesn't grant ultimate power, it releases the baby of the ancient Krakyn, a monster that nearly destroyed Kongland.
They fight the egg, which causes an explosion so strong, it destroys the ship. Everyone is knocked out, but wakes up. Donkey Kong, Mario, and Luigi are on a giant piece of driftwood. The egg is no where to be seen, but then the Krakyn comes bursting out of the ocean. It is now fully grown, and attacks them as the final battle. When they defeat it, the Krakyn dies and slowly drifts to the bottom of the sea. Merry wakes up, and is confused about what happened. They all realize they can use the driftwood to paddle back to the shore. The Kongs are all waiting on the coast, and congratulate them for defeating "that weird-looking lizard" Mario and Luigi head back to the Mushroom Kingdom, as Donkey Kong waves goodbye.
The battle system is like any other Mario & Luigi game. The bros and Donkey Kong can learn combo attacks to battle with.