Unexpectancy. You want "meaning"? This song gives you "meaning".
Part 1. A pretty average final boss theme that encourages you to sweep the floor with Pizzaface's ugly mug. There's also a weird mechanical whirring at one point that sounds like something is malfunctioning. Foreshadowing?
Part 2. Pizzaface opens, revealing he was a mech the whole time. A mech piloted by none other than Pizzaboy, the guy who's plastered his face all over cardboard cutouts, posters, etc. Unexpectancy part 2 is a chaotic, demented song symbolizing the shock of the reveal that Pizzaface was neither pizza nor face, as well as symbolizing Pizzaboy's manic and screwed-up nature as he went off the deep end long ago. Old 30's music is sampled as well, simply because of Pizzaboy's cartoony design.
And, whew. Part 3. Pizzaboy brings back every boss Peppino took down before, for an all-out boss rush. Peppino, of course, isn't the biggest fan of this idea. He doesn't want to practically relive all the things he went through in the past few hours. And... he snaps. He rushes at Pepperman (boss 1) and begins beating the spice out of him, as the music picks up. This "all-out boss rush" turns out to be a display of Peppino's pent-up anger, rage, and pain. The music compliments this well, being a climactic remix of not only Unexpectancy parts 1 and 2, but some of the other memorable songs from the journey. Beating the sense out of everyone who wronged him on this journey, he eventually gets through the last boss and to Pizzaboy for one final fight.
Part 4. The true finale. The song is now a remix of the Freezer level music. Why? Because revenge is a dish best served cold. Slamming Pizzaboy's cheesy head into the roof of the tower and leaving a massive crack, the music fades out, giving you a moment to collect yourself. But Peppino's troubles aren't over just yet. He still has to escape a crumbling five-floor tower and help everyone else (except Pizzaboy) get out too. And as much as I'd love to break down that song, it's Bye Bye There, which is not a part of Unexpectancy.
Thank you for coming to my Ted Talk.