King Dedede heard you were coming and he has called for all the stage bosses to return to Mt. Dedede to protect him. This is going to be your toughest battle yet, but if you've come this far, you mustn't give up. Remember, the people of Dream Land are counting on you!”
— King Dedede and His Crew are Waiting on This Mystical Mountain • Kirby's Dream Land Instruction Booklet
Mt. Dedede serves as the final stage. The main room has four doors, each with a picture of a previous boss. Kirby can enter these doors in any order that he wishes. The doors lead to short versions of the previous stages and then fights the bosses. The door leading to each boss is blocked by a Gordo and can only be accessed if Kirby touches an imposter Kirby. Then Kirby must fight all the bosses, after which he will be able to enter the Dedede Arena for the final bout.
In Spring Breeze, the castle is shortened to only two rooms, the first where Kirby can choose an ability (from an enemy), and the second (and last) one featuring the battle with King Dedede. This time, the arena where Dedede is fought now has an audience watching the fight.
In both the first game and Spring Breeze, the castle ends up airlifted by Kirby shortly after sending Dedede flying out of the palace (destroying a section of the Palace), with Kirby having been transformed into a massive hot-air balloon. And travels over to a field before Kirby reverts to his normal form, and the palace is held aloft in the air by the stars that transformed Kirby, with food raining down.
Mt. Dedede is the final level in Kirby's Dream Land. It doesn't have much of a musical theme as the level is essentially a series or doors to bosses, and Kirby was not expected to stay in the main area for long. The music resurfaced in Kirby Super Star and was used again as the background music in the configuration screen of Kirby Super Star Ultra.
The main bosses, which Kirby defeated in each of the four previous stages, are back again at Mt. Dedede. Kirby will have to trek through four brief "mini-stages" and challenge the bosses again. You can choose the order in which you fight the bosses.”
— Description • Nintendo Power (Volume #39)
The boss theme in Kirby's Return to Dream Land is an extremely heavy remix of Mt. Dedede's lobby theme. This is more obvious when transposed into the key of C.