Cutting the volcano in half became a Crowning Moment of Funny for This Troper because it was the first time Kirby used the giant fish. Nothing is more glorious than seeing kirby cut a volcano in half with a giant tuna.
A minor example of nostalgia from the last level: at the very end of the stage, you can find a secret area containing stars by flying up above the level exit door and entering the background planetoid as a door - exactly the same secret used in Bubbly Clouds, from the original Kirby's Dream Land.
You also get to destroy a space craft while riding a dragon and destroy a giant mecha piloted by a smaller mecha. Really, the second half of the game is just filled with moments of awesome.
The Disc One Final Boss Grand Doomer. This guy doesn't appear until after a Victory Fakeout and gets his own boss theme that is nothing short of epic. You beat down the usual two phases each boss has had up to this point when he shields himself and starts summoning enemies. In the second det of them he spawns, you can get the Ultra Sword. Get it, and a fast paced remix of the Super Ability theme starts playing as you destroy the rock shield, slowly cracking it until it's completely gone. After four hits, you use the Ultra Sword one last time to finish him off in a five hit combo.
In Extra Mode, the bosses are all upgraded by having more health and stronger, upgraded attacks, but are relatively unchanged. Except for the Metal General, who starts out this way... then reveals that he found Dedede's Humongous Mecha HR-D3 and redesigned it into his own mecha, at which point you fight two more health bars to take them down in a very impressive reference to Kirby 64.
The Bonus Boss: You get to fight Galacta Knight, the most powerful warrior in the galaxy, again, and he's more powerful than before. Even better, if you have three friends, you can gang up on him with a four-on-one.