The Empire Porky Building is a 100-floor skyscraper could be considered the "final dungeon" of Mother 3. It is the central attraction of New Pork City and it has all kinds of strange floors crawling with various enemies and inhabited by powerful bosses on the top floor. Lucas and company should enter the building after Miracle Yokuba's defeat in the Sewers.
This is the first floor of the building and looks like a seemingly normal lobby. The room on the right contains a hot spring to revitalize the party before the long trip ahead. On the left is the elevator, which supposedly only travels as far as the 24th floor.
Concert Hall (Floor 24)
It may be full of Pigmasks and even the Fierce Pork Trooper, but the band DCMC is having their last concert here so they don't see any need to try and stop Lucas. The concert is interrupted by Porky's voice over the speakers, demanding that Lucas meet him on the 100th floor. However, Porky tampered with the elevators in the building.
The first of several fake 100th floors, this place is a zoo full of powerful Hippo-Launcher enemies which can only be fought if you run up to their faces. There's only one that actually must be fought, which a Hippo Researcher unleashes on Lucas.
The second of several fake 100th floors, this place is an easy, straightforwards floor with nothing to fight. It is the room where Porky's "Fan Club" meets (more like a harem) and it is also home to one more Oxygen Machine, a special land variety that looks like a Centaur.
Empire Porky Building Bathrooms
The third of several fake 100th floors. This is a maze of bathroom doors and hallways where Lucas will fight Pigmask Majors, Metal Attack Roaches and Men's Bathroom Signs. Towards the end of the maze Lucas may have a second encounter with the Ultimate Chimera. If he can outwit it and sneak into the room it emerged from he'll find an Awesome Ring in a present.
The fourth fake 100th floor holds the last magyspy shell. From what Lucas sees in the shell it is possible to determine who was actually the final magypsy.
The fifth fake 100th floor apparently isn't even finished yet. It's a series of metal and wooden planks crawling with Boa Transistors, Love Walkers, K9000s and Rhinocerockets. An interesting about this floor is that one of the workers says the building is a mix of wood and metal, similar to the title screen of Mother 3, an amalgamation of wood and metal.
Nice Person Hot Spring
The sixth fake 100th floor is actually quite close to the top. It may be the 96th floor of the building. It is a laboratory patrolled by Octobots (a returning enemy from EarthBound) Pigmask Colonels and Mecha-Lions. The Nice Person Hot Spring is the floor where people and animals are brainwashed by Porky. Once Lucas reaches the end of this floor there will be a doorway leading into the next room where there are no elevators but a flight of stairs leading to floor 97.
Lucas vs. Master Mini-Porky. But it's not your typical battle. It's some strange variant of Whack-A-Mole. The enemy manages to hit 10 moles. Lucas should hit 9, losing to Mini-Porky by 1. Only then will the game show host let Lucas continue to the next floor via the staircase.
Another one of the MIni-Porky games. This time, it's a race across purple bridges to the other side. The key is to run ahead of the utterly slow opponent and wait just behind the finish line. Just when Mini-Porky crosses the line, Lucas should immediately follow to get second place and be allowed up the next set of stairs.
This is the final game, and it's worth many more points than the previous two. It involves quickly pumping air into a balloon. Whoever pops the balloon first is the winner. Even though the chance to turn the competition around may seem tempting, the way you get past this test is to fill the balloon to its limits, but let Mini-Porky pop it instead. Only then will the host see Lucas fit for meeting with the real Porky on the 100th floor up the flight of stairs ahead. On those stairs there's a couch so the party can take a quick rest. It would be wise to do so before entering the final floor.
The 100th Floor
As soon as Lucas and the rest of the party enter this floor, the door directly in front of them will be blocked by the Natural Killer Cyborg. After the fight is won, the path leads down a long, long hallway into another room with a boat and a gallery full of all sorts of odds and ends from EarthBound, followed by a small room with an Instant Revitalizing Machine and the EarthBound item known as the Pencil Eraser, which is only there for nostalgia. After going through the door up ahead and climbing the stairs, the party will reach what seems to be the rooftop of the Empire Porky Building. After a surprise ambush from the Porky Bots the party will meet Porky himself, who drops them down a trapdoor, then races down to beat them to the final needle in the caves beneath New Pork City.
The cavern is full of Mineralis and Fenomenos that pose little threat to the party. The only real points of interest are the boss fights against Porky halfway through the cavern which ends with Porky being permanently sealed away inside his own Absolutely Safe Capsule and the final boss battle against the Masked Man, which Lucas must fight alone. There's a hot spring right before the final boss, and in a present somewhere down here Lucas can get the Real Bat.