(The episode begins with Finn falling headfirst from a great height with Fionna on his back, arms wrapped around him.)
Fionna: You gonna do the thing again?!
Finn: Yeah, sis!
(With that, Fionna pulls a ripcord; A parachute comes. They both fall gently towards the surface, and Fionna takes the parachute pack off Finn when they are low enough to do so safely. Finn lands on the ground rolling and does some acrobatics eventually landing in front of Princess Bubblegum; he snaps twice, wiggles his fingers, and claps once.)
Finn: Hey, Princess Bubblegum. Hey, everybody.
(Crowd of Candy People cheers, and everyone starts partying. A bear notices the party. Finn, Fionna and Edana sit down to rest from dancing.)
Edana: (Panting) Man... (Panting) Dancin' is rougher than I thought!
Finn: Yeah... I'm havin' some sweat issues here! I'll go get us some snackety-juice.
(The bear arrives at their table)
Fionna: Hey, man. I'm Fionna. (The bear doesn't respond.) I'm Fionna. (No response) Hmmmm...
Finn: Check it out, Fionna! I got us some peanuts. And punch! (Throws a punch while saying "punch")
(The bear attempts to immitate Finn; Finn laughs. Finn eats a peanut, and the bear responds by eating three peanuts, but it starts choking.)
Finn: (Spits out his peanuts) Choking!! Don't give up on me, man!
(Everyone gasps. Finn quickly takes out the Enchiridion and slaps it on the bear's back, making him regurgitate the peanuts. Everyone cheers.)
Candy Person #24: Whoa, Finn, nice book.
Finn: (Casually) Yeah. 'S pretty cool. It's the Enchiridion--the hero's handbook. (To the bear) Hey, guy, you alright? (The bear softly growls.) Haha. He's all good! Everybody get back to your dancin'!
(The Candy People cheer and resume dancing.)
(The scene changes to nighttime; Finn, Fionna, and Edana are walking home)
Fionna: Uh, Finn? I think that bear is followin' us home.
Finn: Whoa. Haha. I think you're right. Hey, bear, you gonna come hang out with us? (The bear comes nearer.) Whaddaya say, bear? (The bear eats a leaf on his fur.) Heh-heh. Awesome.
Fionna: I dunno, Finn. This guy seems kinda weird.
Finn: Yeah. He's totally weird. Hahaha! (The bear attempts to imitate Finn's laughter.)
Edana: If Finn's alright with him, so am I!
Fionna: (Unsure) Mmmmm...
(Scene changes to inside of the Tree Fort. Fionna is listening to music from "Star Wars".)
Finn: Fionna! Hey, Fionna! (Fionna takes off one of her earbuds) Fionna!
Finn: Come here! Ya gotta check this out!
Fionna: Eh, okay.
Finn: Check this out, sis. This bear is tops blooby! (Fionna rolls her eyes and sighs) Watch this. (Finn inhales and the bear does the same; Finn says, "Choo!" and the bear does the same.) Ya gotta try this, Fionna. He does everything I do!
Edana: Hehe, blooby. I like that word!
(Finn grabs a drink and sucks on the straw. The bear looks for something to imitate with and chews on BMO's leg in resolution.)
BMO: (Laughs) Oh, stop! (Finn pulls BMO away.)
Finn: Haha, come on, Fionna, try it!
BMO: It's awesome!
Edana: Awesome infinity! WHOOHOO!
Fionna: Heh-heh. Um... Yeah, okay. (Grabs a broom and starts sweeping) Sweepy-sweepy-sweepy. Sweep sweep sweep. Sweepin'!
(The bear hits Fionna and knocks him to the ground.)
Finn: (Laughing) He's got me down pat! Heh-hah! Sweeping's weak.
Edana: BUT BURNING ISN'T! Just kidding!
Fionna: (Annoyed) Mmmmmm...
Bear: Sweeping weak.
Finn: Whoa! This guy's alright!
Edana: The war must've made animals like this bear susceptible to easily learning things.
Fionna: This guy just busted me up my chops, Finn!
Finn: Hey, come on, he's just a bear. He don't know nothin'.
Fionna: Mmmm... Yeah, I guess. Well, anyway, it's gettin' pretty late. Probably time for everyone to go back home to their own houses.
Finn: Yeah, I guess you're right, Fionna. It is pretty late. He should probably stay here tonight. (Fionna scowls.) (To bear) You can sleep in the bathtub!
Finn: (Laughs) Brathtub, hahaha! This guy's tops blooby!
Edana: There's that word again! Haha!
(Scene switches to the bedroom; Fionna, Finn and Edana are asleep. Fionna's woken up by sounds coming from downstairs and goes to investigate. She finds the bear dressed up in Finn's clothes and snapping like Finn did earlier.)
Bear: (Claps once) Whaaaat? Hey, Princess Bubblegum. Hey, everybody. (Snaps some more and claps once) Whaaaat? Hey! (Snapping) Hey, Princess Bubblegum! Hey, everybody! (Fionna slowly backs away and falls down.) Whaaaat? Hey!
(Fionna goes back upstairs to the bedroom and rocks Finn and Edana's bunk bed.)
Finn: What are you doing?!
Edana: Wha...is this what an earthquake feels like?
Fionna: Shhh. Come with me. Ya gotta see somethin'. This bear's wiggy, Finn. It's wearing your clothes and dancin' around all crazy.
Finn: That sounds rad, sis.
Fionna: What?! No--Just--! ... Rrrr! (Pulls Finn out of bed)
(Cut to the bear sleeping downstairs)
Fionna: Aw, man! (Finn sighs.) Oh, ya gotta believe me, Finn. I swear, he was, like, all wigged-out, was dancin'... (Desperate noise)
Finn: ...I do believe you.
Fionna: (Pleasantly surprised) Oh.
Finn: It's just, y'know, who cares? Dancing, wearing clothes... He ain't hurtin' nobody. He's just doin' it up, y'know? He's just cool, and he likes my style. That ain't a crime.
Fionna: No. (Chuckles) I guess not.
Finn: Okay. Great. I'm going back to bed. You comin', smart gal?
Fionna: Yeah, okay. (Chuckles)
(They both go back to bed; Fionna looks back at the bear for a moment.)
(Scene shifts to the next morning. Everyone is having breakfast; Fionna leers at the bear (who is still wearing Finn's clothes) and Finn, but doesn't pay Edana any heed. Everything Finn does, the bear does the same, more perfectly this time.)
Fionna: You're not even a little weirded out by this?
Finn and Bear (In near unison; Finn is ahead of the bear by a few words): No, man. He's just doin' his instincts. He's like a parrot or chameleon or something. He's funny!
(Fionna makes an incredibly annoyed face)
Finn: Anyway, I gotta go pick up BMO from soccer. I'll be back soon. And remember: don't eat my special Finn cakes. Finn only.
Fionna: Yeah, I get it. You don't need to tell me that every time you make Finn cakes.
(Finn points at Fionna, implying that he's watching her, and walks out with Edana. Fionna sighs. The bear goes towards the Finn cakes.)
Fionna: Hey, what are you doin'?! (The bear begins eating the cakes.) Why, you little...! Tryin' to set me up, eh? You think you're so smart, but this time, I'm ready. (Pulls out video camera, records bear, and laughs)
(Fionna hums "Smoke On The Water")
Finn: OH, MY GLOB, WHAT?!?! FIONNA! YOU ATE ALL MY FINN CAKES! WHAT THE STINK!
Fionna: Uh, nope. The bear did it, and I've got proof. I taped the whole thing.
Finn: The bear ate all my cakes, and you just sat there and watched him do it?! What's wrong with you?!
Fionna: Ju-- What?! No, man, he was tryin' to frame me, Finn! He's tryin' to steal your identity! Why can't you grock that?!
Finn: (Exasperated noise) He's a bear, Fionna! He's a wild animal! He doesn't know things! He just does stuff! He's cool!
Fionna: Ohh, fine, then that's just great. Then you and M.C. Cool Friend can go stink it up together at your stupid cool Finn party all by yourself, 'cause I'm not going!
Finn: ...Wait. What? What party?
Edana: I wasn't informed of that.
Fionna: What? Your party, sis. Tonight? In the woods?
Finn: (Reading flyer) "Finn'z... bezt... party?" But... I didn't make this flyer.
Edana: Worst grammar ever, I might add.
Fionna: Huh?! Well, who did, then?! (Finn gasps.)
Finn, Fionna and Edana (In unison): The bear.
Edana: I kinda always knew something was screwy with that bear.
Fionna: ...I knew it.
(Scene changes to the aforementioned party. The bear (dressed like Finn) is dancing with the Candy People including Princess Bubblegum)
Fionna: See, bro? He's not just jackin' your style. He's jackin' your whole you! Jackin' yo you up!
Finn: What the what?
Fionna: He got in close and used you. Now he's feedin' nuts to your ex-girlfriend!
Princess Bubblegum: (To bear) Sure! I'll have another... (The bear cuts her off by feeding her a peanut) (Muffled) ...peanut.
Finn: She's not my... (Thinks for a moment) We never went steady. Especially not after the Lemongrab thing. But it's OK, because now I've got Edana, even though we have yet to kiss yet.
(The bear performs the Heimlich maneuver on Princess Bubblegum, and she spits peanuts out and laughs.)
Fionna: He's trying to replace you, and he's already got everyone convinced he's you! He didn't really like you. (Whispering) He used you.
(Finn, angry, marches up to the bear)
Bear: Tops blooby! Tops blooby. Tops-- (Finn pulls the bear's mask off)
Finn: Not cool, man. (Everyone stops dancing.) You're not me. You're just a bear acting like me. NOW GET OUT OF HERE OR I'LL KILL YOU LIKE THE ANIMAL YOU ARE! (The bear starts crying and quickly leaves.) (To everyone else) It's okay, everyone. The imposter is gone.
Princess Bubblegum: Finn... nobody really thought the bear was you.
Finn: (Saddened) Wait... what?
Princess Bubblegum: We just thought it was one of your jokey-joke-jokes. And you wondered why we never dated. THIS BEHAVIOR OF YOURS!
Edana: YOU SHUT THE HELL UP, YA WALKING PIECE OF CHEWING TOBACCO!
Princess Bubblegum: TAKE THAT BACK!
Finn: STOP! Must we fight?
Princess Bubblegum: I guess not...
(Finn, Fionna and Edana run after the bear.)
Finn: Hey! Hey, bear!
Fionna: Wait up, guy!
Edana: Hold up!
Finn: Hey. I... I didn't mean to make you feel so bad about yourself. I'm really sorry about that.
Fionna: Me, too.
Edana: Me three.
Finn: But... you're a super-rad bear, so... why not just be you?
Bear: (Crying) I... want... be... hero... like... yooouuuu!
Finn: (With pity) Awww...
Fionna: I guess he's got a heart of gold after all.
Finn: Hold on, bear. I got something for ya. It's the Enchiridion, the hero's handbook. Everything you need to know about being a hero is in this book. Take it, and learn.
Fionna: (Whispering) Finn, are you nuts?! We can't give that book away! It's, like, crazy-important! If that thing falls into the wrong hands, it's Doomsday for Ooo! Remember what Mannish Man said?
Finn: Whatever, sis. We never use it, except for, like, sitting on it when the grass is wet and stuff. (To bear) Drink your fill of knowledge. Someday, you'll be a great hero.
Bear: Thank you, Finn. Thank... yooouuu...
(The next scene shows the bear travelling far, far away with the book on a bike. Eventually, he reaches a rocky mountain and climbs it with the book in his paw. He arrives at a cave and roars. A voice answers.)
Voice (Ian McDiarmid's): Did you bring the book?
(The bear holds up the book. The Snail, still possessed by the Lich, comes out of the shadows)
Snail (the Lich): Yessss... One step closer. Soon, my master plan will be complete, Finn will be dead, and I will do what Iran couldn't do! RULE THE WORLD!!! (Cackles) But before that, to sabotage one of Princess Bubblegum's next experiments. The one she calls...Goliad.
(The episode ends...)