[It all started at the daytime. April, Casey and Irma are walking down the street.]
Irma: I know they claimed that pizza was gluten free, but I definitely tasted gluten.
Casey: Thanks for hanging out with us on our date, Irma. We really needed a chaperone.
Irma: Anything I can do to help.
April: Um, who said this was a date, Casey?
[A mouse runs past.]
Casey: Yah! What the..
Irma: I can't believe someone as big as you is afraid of a little rat.
[Cat screeches at the rat.]
April: And I can't believe that rat was afraid of this adorable little kitty. [she picks up the cat] Aw.
Irma: I mean, rats are relatively harmless. They also share many similarities to humans, which is why they're used in scientific experiments.
Casey: [annoyed] Does she ever shut up?
April: [looking at the cat] Little kitty doesn't have any tags. We can't just leave her here.
Irma: Don't look at me. I'm more of a rat person.
[Something clattered as April and Casey leave.]
April: Catch you later, Irma. Got to find this kitty a home.
Irma: Sure. Ditch me again. One of these days, I'm gonna find out. Where you two are always running off to, and then I'll-
(Something sneaks behind her and roars; Irma turns around and screams.)
[theme song]
Leo: I don't know, Master Splinter. This doesn't seem fair.
Splinter: [with blindfold on] I assure you, it isn't.
(Leo draws katana, and attacks, Splinter dodges, Leo misses, Raph, Donnie and Mikey laugh.)
Mikey: Oh, man.
Raph: A swing and a miss.
Splinter: Blind fighting is more than honing your other senses. It is about perception and giving the illusion of control.
[Leo attacks but misses again]
Splinter: You may think you have the upper hand. In the situation, but.. You do not.
[Leo charges but Splinter dodged his attack and knocked Leo down. Donnie, Raph and Mikey began to laugh.]
Mikey: Looks like someone needs a shower.
Raph: How's that floor tasting, Lame-enardo?
All: Ow!
[The rat mutant hits them on the back of their heads with the sword.]
Splinter: It is not hard to sense loudmouths.
[Suddenly, Splinter groans, taking off his blindfold and his eyes turn red.]
Splinter: [brainwashed] You turtles! You will all-
[Splinter hesitates]
Leo: [concern] Master Splinter, are you all right?
Splinter: I am sorry, my sons. This is... Something is wrong. I must meditate. We will continue this training another time.
Mikey: Yo, did you see that? Sensei gave me the crazy eyes.
[Later in the lab, Mikey is eating ice cream.]
Mikey: So I wonder what got into Master Splin- Aah! Aah! Brain freeze!
Donnie: Mikey! You're making a mess! Keep your ice cream away from my experiment. I'm trying to make Retro mutagen.
[One of the ice cream droplets landed on the mutagen.]
Donnie: Always messing up my stuff.
[April arrives with the cat]
April: Hey, guys. What's up?
Donnie: April! And Casey.
Casey: Donatello.
April: I came to see if you guys could look after this.
[Amazed, Mikey takes the cat.]
Mikey: Aw! Look at you! Coochiewoochiewoochie! [he plays with the kitty] Can we keep her?
[He sets her down while the cat starts licking the ice cream.]
Donnie: You know, Master Splinter is a rat.
Casey: Yeah, what if that cat goes nuts and attacks him? She could feed off his body for months.
Donnie: You know, there is something seriously wrong with you.
[Cat meows. Mikey saw that the cat licking the ice cream earlier was licking the mutagen!]
Mikey:[Gasps] No, no, no, no, no, no!
[The cat started to melt and started to change into a liquid substance. Horrified, Mikey lowered his head.]
Mikey: Oh, what have I done?
[Slowly, the substance started to change into a cat but with ice cream color pelt. It turned into a mutant. Mikey's eyes were wide.]
April: Everything okay, Mikey?
Mikey: Yeah, yeah, it's cold. I mean cool. Everything's cool. Cool like ice cream. Ice cream's cold. [Chuckles.]
[Mikey runs away, leaving Don and April bewildered. In the dojo, Splinter is meditating, then the creepy music plays and then red eyes appear in his vision, he is struggling, until he realizes it's the Rat King.]
Splinter: No. I defeated you. You were gone.
[Splinter runs away on four arms as rat king's vision after him.]
Rat King: I am never gone. I live because you live.
Splinter: Get out of my mind!
[The blue eternity reveals itself open, revealing human Splinter, Hamato Yoshi.]
Rat King: I'm even deeper than your mind. I'm inside your very soul. You will give everything to your King! Your Rat King!
Splinter: No! You have no control over me.
Rat King: I have what I came for.
[Mikey puts Ice Cream Kitty into the freezer.]
Mikey: Don't worry, my little friend. This will keep you from melting. Until I use my scientific genius to figure something out. [Kitty meows and licks him] You taste so good, my little ice cream kitty.
Leo: Mikey?
[Mikey closes the fridge, grains of seed landed on his head.]
Mikey: Uh, I didn't do it. I swear I never touched it, and-
Raph: What are you babbling about?
Splinter: [Grunts.] Need ice... for my head and possibly a Cheesicle.
Mikey: You can't do that! No, Sensei!
Splinter: [creepy and angry] No? You tell me no?
[Splinter becomes brainwashed and tries to attack Mikey. Everyone ducked.]
Casey: This is not helping my whole rat thing.
Leo: Help him!
[They pin Splinter down. but he escapes. However Splinter flinged everyone off him.]
Rat King: I've got what I came for. Soon New York and the world will be mine!
[Splinter falls]
Leo: Sensei, are you okay?
April: What happened?
Splinter: The Rat King has returned.
[Meanwhile, the white mouse started to climb up to where the Rat King is.]
Rat King: Go forth, my rat warriors. You know what you must do. Attack!
[All over the town, giant rats started to attack everything. Rain begins to fall as everyone screamed and run for their lives.]
Rat King: Look at it, Aristotle. Such beautiful chaos. I can see it through every pair of rodent eyes. Soon, this world will belong to our rat brethren.... With me as King.
Joan: This is Joan Grody reporting live from Bleecker street, where giant rats have emerged from the sewers. These revolting rodents are snatching people away on this edition of Grody to the Max. [Screams.]
Casey: Giant rats? Giant... rats?
April: Maybe you should sit this one out, Casey.
Leo: We could really use your help, Sensei. Last time you took that creep down with one punch.
Splinter: Last time was different, Leonardo. The Rat King has grown too powerful. I do not fear for myself, but for what he could .....Force me to do.
Rat King: The human species is coming to an end. It is time to advance the next phase of evolution. Rodents shall rule! What?
[Mikey is being pulled while the turtles ride the go kart.]
Mikey: Why do I have to wear the cheese?
Raph: We have to lead them away, and you're awesome at being bait.
[Casey follows after them on his bike.]
Casey: This is the worst thing ever!
[The rats started to chase him.]
Mikey: Waaah! Faster, faster, faster!
[The shellraiser arrives]
Leo: Sorry I'm late.
Rat King: Revel in the madness, my brother. There is room for you in my new world.
Splinter: No! Get out of my head!
Rat King: It doesn't matter. You already belong to me. You just don't know it yet.
[Mikey climbs onto the go kart.]
Mikey: Aah! They're gonna get me!
[One of the rats lunged at the go-kart and got hit by the trash balls. The rats started to corner around the shellraiser.]
Leo: A little help here, guys?
[Casey drives by and starts to use his marbles to trip the rats down then used his flamethrower, making the rats avoid the flames. Finally he released fireworks at the rats, scaring them off and knocking them down.
Casey: Yeah! No rat messes with Casey Jones!
[A rat charges and drags Casey. The teen tried to punch it away but its grip is too strong.]
April: Casey! Guys, turn the kart around!
Raph: Let's split up!
[They split into different directions.]
Rat King: Caligula, come to me! Come, my brothers. Claudius, Nero, Commodus, the rest of you, back to the lair! We have enough humans.
April: Casey! No, you don't!
[April tried to pull the rat's tail but it whips her and leaves through the sewers.]
Donnie: April! Is Casey-?
[Brokenhearted, April hugs Donnie.]
Irma: Hey, are you okay? Mister?
[Casey wakes up in a cage with Irma.]
Casey: Aah! Oh, great. [Deep voice.] Uh, I'm fine, miss. Where are we?
Irma: The sewers. We're prisoners of the Rat King.
Rat King: Welcome, esteemed guests. There's no need to fear. I will not hurt you. That I promise.
Casey: Let us out of here, you freak!
Rat King: All in good time. These were simple, ordinary rats. Until I transformed them. With my special mutagenic growth serum. But these were not the soldiers I was looking for. I have just unlocked. The secrets of the ultimate army. Rat people! And you, my friends, will become that army!
[Everyone becomes scared and Irma faints into Casey's arms.]
Splinter: The Rat King peered into my mind to see what makes me unique. With that knowledge, he will create an army of rat people.
Leo: We got to stop him, Sensei.
Splinter: I told you, he is too powerful even for me.
Leo: But, Master Splinter, if there's one time we could use your help, it's now.
Splinter: Enough! I will not put you in danger again.
April: We believe in you, Sensei. We need your help and so does Casey.
[Everyone started to prepare for battle.]
Mikey: Are you ready for the most dangerous, crucial mission of your life? [Kitty meows.] Aw, Kitty. Then let's do this!
[In the rat king lair.]
Rat King: That's right, Aristotle. Every time one of my rat people bites a human, they will infect them, causing the mutation to spread. And spread until every human being. In this wretched world transforms into one of us. What's that you say? The serum's not perfected? What do you mean?
[The man that The Rat King tested on turns into a disabled monstrosity. A form of rats piled together into one ghastly thing.]
Rat Freak: Cheese. Give me cheese.
Rat King: Well, not every experiment can be a success. But this new serum will work. Perhaps we should test it. [Rat squeaks.] You're right, Aristotle. She is the perfect test subject.
[Irma faints again]
[The turtles and April arrive at the rat king lair.]
April: There's Casey. He's alive. And Irma?
Donnie: We can't let the humans see us, April. You have to free 'em.
Leo: Sensei?
Splinter: It is time the Rat King is dethroned.
Leo: [hopefully] I knew you wouldn't let us down.
Splinter: If I should lose control, you do what you have to do.
Mikey: Nothing's gonna happen 'cause I got my supersecret weapon. Yeah.
Leo: Let's go!
[They are ready, they began to climb up to the cages as April kept an eye on the sleeping rats. Leo sees the Rat King, he is about to murder and stab him by throwing the scalpel at him. Rat King stops, right before Leonardo can shoot him down, Splinter grabs his hand, much to his shock. He learns that he has red eyes, Leo glares in shock at Rat King, who's laughing maniacally, indicating he knows that Leonardo's going to kill him, due to his rat Aristotle...]
Splinter: No! Get out!
Rat King: You're mine now, Splinter. Destroy your sons... One by one!
[Leo gets pinned down by Splinter.]
Mikey: Forget that, Rat King! Oh, yeah! Ice cream kitty, away!
[Michelangelo throws Ice Cream Kitty to Rat King and she starts attacking the man furiously. Splinter gets free from the brainwash process and lets go of Leo. Donnie is shocked by the new mutant.]
Donnie: Is that April's cat?
Mikey: Absolutely not.
Rat King: Aah! Destroy them!
[Rat King gets down and Splinter is in pursuit.]
Rat King: Go, Caligula! Hyah!
[Splinter started to chase him]
Splinter: You run like a coward when not in control!
Rat King: Who said I'm not in control? Attack!
[The rat horde follow.]
[In the lair, Mikey held a cheese as the rat sniffs it. Every time it sniffs, he punches him.]
Mikey: Smell the cheese. Hyah! Smell the cheese! Hyah! Come on, smell it!
[The others continue fighting. Leo punches the rat and Raph comes to his aid.]
Raph: Leo!
[They shove the rat down the hole. April pulls down a lever and frees Irma and Casey.]
Casey: Yes! Finally free!
Irma: April! How did you find us? Did you follow the trail of rat droppings? It has a unique aroma of....
Both: Not now, Irma!
Casey: Let's free the others and get out of here.
April: Irma, give me a hand with their cages.
[The three humans lower the cages down and free them while Irma accidentally activates a machine.]
Irma: Oops.
People: Run! Get out of here! Yes! Yes!
[Donnie is cornered by a few rats until he was knocked off and starts to fall until Mikey saves him.]
Mikey: Got you, D.
Donnie: What? We're gonna talk about that later.
[The Rat King is in the dark city of New York. Splinter begins to follow him.]
Rat King: Fall!
[Splinter loses his grip and grabs onto the pipe.]
Splinter: No. I will not let you escape this time.
[He climbs his way.]
April: Hurry! Everyone, run! We'll lock the door!
[A rat appears about to attack but Donnie knocks it away.]
Donnie: You guys get everyone to safety. We got this covered.
April: You always do.
[In the sewers, Irma and Casey run while April joins them.]
Casey: I'll be fine if I live the rest of my life. Without seeing another...Rat.
[The rat roars]
Casey: I've had about enough of you.
[Casey begins to knock the rat out of the way. April and Irma look at each other.]
Mikey: Easy, Mr. Rat.
[Ice Cream kitty starts to attack the rat. The rat tries to eat her but spits her out.]
Mikey: Ice cream kitty! [Gasps.] You're my hero! And you taste so good.
Raph: I think that's all the rats.
Leo: But what about Sensei?
[Meanwhile, Splinter had encountered the Rat King.]
Rat King: That's right. Bow before your Master, rat. There's nothing you can do that I can't see coming.
Splinter: So you still think you are in control of the situation. [knocks the rat off the Rat King's shoulder, and into the void, killing the rat.]
Rat King: Aristotle! You'll pay for that. I can still see through your eyes. [He notices Splinter has his bandanas, much to his shock] What?
Splinter: How about now?
[The Rat King is now in darkness]
Splinter: Control is an illusion.
Rat King: Where [gasps.] Are you? Ah! Aah!
Splinter: It can be even more blinding than the inability to see. It can..
[The Rat King tries to strike him, and falls into the void to his death!]
Splinter: Send you over the edge. Goodbye, my King.
[Splinter takes off the blindfolds and watches triumphantly as the episode ends.]