SpongeBot SteelPants is the final boss from the console and Game Boy Advance versions of the game, Battle for Bikini Bottom.
On the console version, he looks like a bigger, metal version of SpongeBob SquarePants in Karate gear, with jet flames coming out of his pants (allowing him to fly and damage SpongeBob through contact) and transparent glass-eyes that show the insides of the robot. Its mouth is speaker shaped in its vein when exposed.
Before the first phase of the boss battle, the robot possesses nine, green-colored energy generators in the form of lights, on points of its body (one on each palm, one on each corner of his face, one on each side of its head, and one on the tip of its nose). These generators are its weak-points which SpongeBob must target with his abilities, and once one is shattered, it cannot be damaged again.
On the GBA version, it looks the same except he has a Krusty Krab uniform hat, glowing red eyes, and Spat replacing its right hand (much like the Hash Slinging Slasher), and has purely metallic arms in a dark coal shade (the other hand is a clamp). He also has a notable red light as a signal receptor/antenna on the back of its head, and is also much smaller than the console counterpart.
After his defeat during the first battle, SpongeBot started to have an exhausted fit, flailing away most of the floating platforms in the arena, before its arms fell off and collapsed on SpongeBob, causing its helmet to fly off towards the screen. Planning to have married the robot the week after, Robo-Plankton becomes distressed, and repairs the robot to take on a larger and stronger form.
SpongeBob's efforts were soon shown to be for naught as SpongeBot soon suddenly grew a pair of Anchor Arms (seen in MuscleBob BuffPants), and Robo-Plankton heads into its head through the robot's "left ear"; thus forcing SpongeBob to dive in after the smaller robot to destroy the metal monster from the inside and starting the second part of the battle.
Once SpongeBob destroyed all of SpongeBot's fuses and neutralized his brain, he begins to shut down. As SpongeBob and Robo-Plankton are forced out, his arms begin to deflate, and he hits the wall, falling over, crunching up, and shutting down for good.
Battle for Bikini Bottom Cutscenes
Patrick: Look at that guy, with that big square head, and those short-shorts. It's the most hideous thing I've ever seen!
SpongeBob: Wait! That hideous thing looks like me!
Squidward: I always knew SpongeBob would be the death of me!
Sandy: Jumping jelly beans, a robot SpongeBob!
SpongeBob: There is something definitely funny going on here... [Looks at mime] and I don't mean you. Something else funny. (Gasps) Plankton! You're behind all this, aren't you?
Plankton: Yes, it was me all the time! Behold! The Duplicatortron. I registered the name, so don't think of ripping me off. With this I can make the robot-copy of anything. I was going to make an army of loyal robots that would obey my every command.
SpongeBob: But they're running amok!
Plankton: I uh... I forgot to set the switch to 'Obey Plankton'. But now that's daddy home, I can fix that (Places obey sign over setting). What's wrong now? It should be working!
Robo-Plankton: It is working! They're obeying me.
Plankton: I knew I shouldn't have made a copy of myself. But I was just so cute.
Robo-Plankton: You've interfered with my plans for the last time! SpongeBob meet SpongeBot.
SpongeBob: Hi! How do you do? Allow me to introduce my friends: Patrick, Sandy...
Robo-Plankton: Enough! Prepare to meet your doom!
(SpongeBot malfunctions and falls-apart)
Robo-Plankton: No! You dolts have destroyed my beautiful bride! We were supposed to get married next week.
Sandy: Did he say marry?
Robo-Plankton: I'll repair you baby! (SpongeBot grows Anchor Arms)
Patrick: Oh no! I'm shrinking.
SpongeBob: No Patrick. I think the robot is getting... BIGGER!
Patrick: SpongeBob he just flew into your head!
SpongeBob: Well then I am going to follow him into my head! I mean into my robot version's head. Which is like my head, but bigger, and more metallic.
Plankton: Will you go already!
Spongebob: Here I come Robot-Plankton!
Squidward: This is just getting too weird for me.
Sandy: SpongeBob you did it!
Patrick: What'd he do?
Squidward: What?! Oh... Um.
Plankton: All my plans! Ruined! That does it, I'm becoming a lawyer.
Robo-Plankton 1: You haven't defeated me yet! I still have lots of robots all over Bikini Bottom! I'll summon them all, and then you'll see... (Bumps into Robo-Plankton 2) uh oh.
Robo-Plankton 3: Oh yeah? I'll destroy you plus one!
Robo-Plankton 4: Well I'll destroy you plus infinity!
Other Robo-Plankton 1: Shut up you stupid robot!
Other Robo-Plankton 2: Who are you calling stupid?
Other Robo-Plankton 3: I went to community college! You over-sized coffee grinder!
Other Robo-Plankton 4: Oh yeah? I'll show you!
Other Robo-Plankton 5: Come here and fight like a mono-cellular organism...
SpongeBob: Well Plankton? I hope you learned your lesson.
Plankton: Oh I certainly did! Next time I'll get it right (Chuckles maniacally).
Patrick: (Steps on Plankton) We won! Who wants to get ice cream?
SpongeBob: I do! I do!
Sandy: Need I remind you all that there are still robots making a mess of Bikini Bottom?!
SpongeBob: Sandy is right!
Patrick: I thought she was a squirrel.
Squidward: I'm being punished. I don't know for what, but I'm being punished.
SpongeBob: There's still work to be done out there. Mermaid Man and Barnacle Boy wouldn't stop! And neither will I! We can't rest until Bikini Bottom is safe!
Inside the Chum Bucket
The battle takes place inside the Chum Bucket, wide in scale, with floating platforms, spring boards, and an absent ceiling. SpongeBob can fall below without taking damage to retrieve underwear when low on health, and then return to the battle with the spring boards. Robo-Plankton will always attack non-stop until SpongeBob returns to the floating platforms.
During the beginning of the battle, SpongeBot will perform his Karate Slash where he will slash over the platforms, making his palms the most vulnerable to SpongeBob's attacks. After taking two hits, SpongeBot becomes unconscious, immune to attacks and Robo-Plankton will temporarily attack SpongeBob, until he is hit. SpongeBot will not revive unless SpongeBob returns to higher and floating platforms. When SpongeBot's health is reduced by a third he will introduce the Karate Chop in his attacks.
SpongeBot will begin to become more aggressive, and start to make chops on the floating platforms SpongeBob is standing on. Every time he loses an energy generator, he will perform two Karate Chops, finishing with a slash across the platforms. Down to only 4 points on his health bar, SpongeBot will become unconscious once again, while Robo-Plankton tries to attack SpongeBob for a second time. Once he regains consciousness, SpongeBot will fling words at SpongeBob that can hit three platforms.
In the final phase, SpongeBot will perform his Karate Yell, three Karate Chops, finishing with a Karate Slash. Each time he takes damage from SpongeBob, he adds more Karate Chops and Karate Yells in his attacks. When reduced to only one life point, Robo-Plankton will attack SpongeBob for the final time during this battle. With only one generator left, SpongeBot will be defeated with a final and single attack.
Inside the Robot
Once all the weak-points on the robot are destroyed/its HP bar is fully depleted, SpongeBob must go inside and shut down the robot by neutralizing its brain. Inside of SpongeBot's head, there are many platforms and Duplicatron 2000s which will produce various enemies to stop SpongeBob. Along with this, Robo-Plankton will occasionally pop up and try to attack SpongeBob as well. To shut down the metallic monstrosity for good, SpongeBob will need to break all 7 of SteelPants' fuses (which are thin glass tubes circulating electricity) using his bubble weapons.
Brain Cell Fuses
First Cell: Guarded by Tar-Tars and Ham-mers. Once the fuse is unlocked, you can simply destroy it with a midair Bubble Spin.
Second Cell: Protected by Chucks and G-Loves (produced by a Duplicatron from a far away platform which must be destroyed by the Cruise Bubble). This cell is hovering above the ground, so use a Bubble Bash to smash it, but from a far enough distance, a Cruise Bubble can break it if angled upward enough.
Third Cell: Patroled by Fodders and Monsoons, produced by a Duplicatron on a floating platform. This one is lodged into a grate and can only be destroyed with a Bubble Bounce, though it is possible to walk into the grate and hit it with a normal attack.
Fourth Cell: Protected by Monsoons, with a Duplicatron that produces Ham-mers and Chuck. The fourth cell is enclosed in electric fencing, and SpongeBob must use Bubble Bowl or the Cruise Bubble to break it.
Three remaining Cells: The last three cells are held in the core of the robot's brain and are guarded by Robo-Plankton. Use the Cruise Bubble to take Robo-Plankton down after he shoots his lasers, and to steer it down all three tubes, to destroy the cell at the end. There are a total of three bouncing platforms that Spongebob can use to relocate around the brain, while Robo-Plankton appears everytime the player lands on a new platform, or if the player stays around one of them for too long (where he must be hit again for possible breathing room).
Karate Slash: It can swing one of its arms over several platforms via a horizontal chop and freeze in place for a while, leaving him vulnerable to attacks. Oddly enough, when chopping with its left arm, it chops more inward than with its right arm. Hitting one of its weakpoints during its frozen state and when a tri-section of its health bar is two units depleted will cause it to recoil with its hand smacking his own face into unconsciousness.
Karate Chop: The robot can karate chop Spongebob, causing him to fall, and take damage while the platform flips. The chop reaches all the way to the bottom central platform.
Karate Yell: The robot can scream "KAH-RAH-TAE!" and shoot these words towards the platform Spongebob is standing on, then shoot towards the two other platforms beside him. During this phase, its weak-points one the lower body and its nose are vulnerable to most of SpongeBob's attacks.
Krabby Patty Bomb: Makes a Krabby Patty Bomb and throws it at the ground via lobbing his spatula hand forward. These are meant to be eaten by Mystery and spit back out at the robot to damage it. Thus, if Mystery is abandoned mid-battle, then SpongeBot battle will be impossible to win.
This is the only major boss in the game (console versions) where only one character is playable.
Even though Robo-Plankton is seemingly the main antagonist of the game, SpongeBot is the one who is considered the final boss.
Several of its weak-points can be hit by all of SpongeBob's other moves (Bubble Bash being least likely), and not just simply with his Cruise Bubble. However, while they can be hit at anytime, hitting them while the robot about to attack is not a recommended option.
SpongeBob can use Bubble Spin or Bubble Bounce, after SpongeBot's palm is exposed when frozen in place.
SpongeBob can also use the Bubble Bowl to hit SpongeBot's nose after while using his Karate Yell.
There is an odd glitch where the player can beat SpongeBot in at least two hits. If the player gets SpongeBot to chop at the platform (attack begins after second hit) and avoids the attack while staying on the platform, SpongeBob will be flung into the air and the scene that plays when the SpongeBot is first defeated is triggered, thus ending the fight.
The first part of the battle is the only battle in the game with no split-phases in between, as SpongeBob is the only usable character here. This is also the only major boss battle to involve a pit that is "out-of-bounds", as normalls SpongeBob dies out of bounds, causing the whole battle to reset (with SpongeBot having full HP and all generators in tact once more).
In the second portion inside the robot, if not carefully positioned via one of the re-locating midair spring boards around the robot's brain, it is possible to have SpongeBob return to the starting platform of the level once, as it is below one of the said spring boards around the brain.
If SpongeBob is hit by the robot's Karate Chop, Karate Yell, or Robot Plankton's energy cannon during the first part of the fight, SpongeBot will mimic SpongeBob's signature laugh in its robotic voice, complete with placing its hands on its front. Via its horizontal chop however, it will not taunt him and will stay frozen until enough time passes as usual.
In some variations of the console versions, the lights from SpongeBot's energy generators on one of the sides of the robot's head will be misplaced, with the light jammed from the inside.
The cutscene that occurs when the robot is first encountered only plays once per playthrough, per file, on some variations of the console version.
Inside the robot during the second phase of the battle is noticeably much larger than in the cutscenes and during its initial battle. SpongeBob and Robo-Plankton are just as big as its pupil outside of the said playable phase.
Also, if a custom camera mod is used for the second cutscene, SpongeBot does not actually increase in size, despite the dialogue and the playable version of inside of its head.
During the final cutscene of the game after it's been defeated, its eyelashes disappear. Its energy generators also disappear during the defeat of its first phase, and during some portions the intro cutscene if a camera mod is used. The said generators also are not visible on the robot's HP bar portrait.
While unconscious, SpongeBot will only continuously face SpongeBob if he's on the lower platform. Falling off while it is active will cause its attack cycle to be halted and will reset when SpongeBob bounces back up to the higher platforms.
If the weak-points are hit at any other time outside of being frozen from its horizontal chop, then SpongeBot will perform its normal pain animation always, even if it's left with one portion of a tri-section of its HP bar left.
The second form of the robot with the Anchor Arms was originally to be fought in previous builds of the console versions, along with previous trailers showing brief moments of the battle, but it was eventually scrapped from the final build of the game, for unknown reasons.