Duped is the second episode of Ben 10: Ultimate Alien.
Forever Knights try to invade the museum using an alien paramilitary tank, but they're interuppted by Ben as Rath. Gwen calls Ben and tells him that he is missing Julie's tennis game. Ben sees the Forever Knights running away and tears apart their tank, then heads to the stadium for Julie's game.
When Julie is about to begin her match, Ben shows up and makes a huge hit of himself and blows her concentration. Julie and Gwen get mad at Ben for showing up late. Kevin wants to investigate why the Forever Knights tried to rob the museum, but Gwen disagrees on going, stating that they're probably stealing some tech to rule the Earth. Ben also wants to catch the Sumo Slammers movie, but Gwen tells him not to. She tells Ben he can't be in two places at once. Ben then comes up with a plan and transforms into Echo Echo and splits in three, then turns back and this time there are three Bens. One of them is the real Ben, the second is the honest, intimate Ben, and the third is the immature and arrogant Ben. The real Ben goes to the Sumo Slammers movie, the honest Ben goes with Kevin to investigate the Forever Knights robbery, and the arrogant Ben stays to watch Julie's match. The Forever Knights, meanwhile, and their king Urien find a shortcut to the museum to claim ultimate power.
Unfortunately, Arrogant Ben keeps embarassing Julie, much to the annoyance of her and Gwen, Honest Ben keeps annoying Kevin with about what he thinks of him, but Real Ben so far is having a good time at the movies.
Kevin and Honest Ben fall into the basement of the museum and meet Urian and his Forever Knights. Urien makes his minions fight Honest Ben and Kevin, where he is still annoying Kevin due to his personality. They knock Urian's minions out and find out that he is after an ancient Aztec alien battle armor, which he uses to attempt kill Honest Ben and Kevin. Real Ben and Arrogant Ben hurry to the museum to help Honest Ben and Kevin. All three Bens change into Big Chill, Upchuck and Cannonbolt to fight Urien but fail due to their weaknesses and differences. So all the Bens change into Echo Echo, and go back into one Ben. Ben uses Lodestar to finally stop Urian. Even though Julie won the tournament, she is still mad at Ben thanks to his immature clone embarassing her. She kindly asks Ben to make it up for her by taking her to see the Sumo Slammers movie, but Ben admits that he saw it during her match, which causes Julie to become instantly angry. She and Gwen storm off in disgust along with Kevin, leaving Ben to repent for what he has done in order to gain back their trusts.
- Ben Tennyson
- Gwen Tennyson
- Kevin Levin
- Julie Yamamoto
- King Urian
- Forever Knights
- Echo Echo
- Humongousaur (used by Sensitive Ben)
- Big Chill (used by Real Ben)
- Upchuck (used by Arrogant Ben)
- Cannonbolt (used by Sensitve Ben)
- Ben: I'm glad you won your tournament, Julie.
- Julie: (sarcastically) Yeah, thanks.
- Gwen: You should have been there, and by that I mean you should have been there.
- Ben: Ok, Gwen. (scowls)
- Julie: Ben, I know you were off fighting bad guys. I was upset. But, I guess that's a deal when you decide to date a superhero.
- Ben: (trying to please and calm down Julie) Julie, I promise, I'll make it up to you. Whatever you want to do, I'm there, just name it.
- Julie: (calmed and pleased, ready to give Ben another chance) Well, maybe we can go to Sumo Slammers: The Movie together.
- Ben: Actually, I, uh... already saw it.
- Julie: When...?
- Ben: Uh.... during your match..?
- Julie: Well?! That's just...... ooh. (angrily storms off)
- Gwen: Nice. (storms off after Julie)
- Kevin: Man, you're so insensitive. (walks out too, leaving Ben alone in the stadium to repent on what he did)
- Arrogant Ben: (yelling to Julie's tennis opponent) Hey, other girl! You're a terrible tennis player and my girlfriend's gonna kick your butt!
- (silence, then the crowd starts yelling)
- Referee: What's happening up there?
- Julie: Uh, that's my... boyfriend.
- Referee: (sarcastically) You must be very proud.
- Humongousaur: (singing) Humongousaur!
- Kevin: Never do that again.
- Humongousaur: Just trying it out.
- Kevin: Ben! You've always been kinda girly but today...
- Sensitive Ben: Yeah?
- Kevin: You're creeping me out!
- Sensitive Ben: ....I understand, I'm truly sorry.
- Kevin: Stop understanding. Stop apologizing, stop telling me about you're feelings! I just wanna find some Forever Knights and pound them.
- Sensitive Ben: Hmmm... Interesting.
- Kevin: Cut that out!
- (Two forever knights drive a tank towards the museum)
- Forever Knight: Right then, we go in fast, grab what we came for and get out.
- Forever Knight: Charging the cannon now.
- (The Knights aim the tank's cannon at the museum door)
- Forever Knight: This'll rip that door open like it was made of tissue paper!
- Rath: (Rips open the top of the tank) Let me tell you something, Forever Knights; nobody's ripping open nothing except Rath! (One of the Forever Knights shoots at Rath) That's your first mistake; when you shoot Rath, you just make Rath mad!!! (He is about to attack when his phone rings and he answers it) (Lowering his voice) Helloooo?
- Gwen: Ben, where are you? Julie's in the middle of her set!
- Rath: Let me tell you something, Gwen Tennyson; I was on my way there when I saw this tank pull up at the museum and--
- Gwen: (Cutting Rath off) I don't care, get here! (Hangs up)
- Rath: That was harsh. (Raises his voice again) Now, where were we?! (Looks back into the tank to find that the Forever Knights are running for their lives. Goes mad and starts throwing parts of the tank at the Knights.) (Talking to some old men on a bench who are acting as though nothing is happening) What?! It was already busted! (Walks off.)
- Girl: I'm your biggest fan!
- Immature Ben: Well, that makes two of us.
- Reporter: Ben, any comment on Will Harangue's editorials? He says you're a menace!
- Immature Ben: Yeah? I say TV's a dead medium. Sorry man, you know it's true!
- Gwen: Where have you been? Julie's match is about to start.
- Immature Ben: I'm here. Why don't you put a sock in it?
- Gwen: Whoa. What's with all the attitude?
- Immature Ben: I'm Ben classic. Miss me?
- Kevin: If I weren't running for my life, I'd totally demand an explanation. (indicating the 3 Bens)
- Ben: Nice game, Julie.
- Julie: How would you know? (walks away)
- Ben: What? What did I say?
- Gwen: It's what you did, Ben. You were late, and when you finally show up, you made a big entrance and completely blew her concerntation.
- Ben: I can't help if I'm famous, right? (waves to the crowd; Gwen glares at him)...I'm sorry. It won't happen again.
- Gwen: It better not. The finals are in three hours. That should be enough time for you to figure out how to make this up to her.
- Ben: (to Kevin) Any suggestions?
- Kevin: Yeah, there's a plan - ask me for girlfriend advice.
- Gwen: What are you doing?
- Ben: I was thinking that while we were waiting around, I could go and catch "Sumo Slammers: The Movie."
- Kevin: You're either the bravest man alive or the dumbest.
- Ben: What?
- Kevin: Okay, the dumbest.
- Kevin: Ben, do something!
- Humongosaur: Why me?
- Kevin: Because you're a giant, indestructible dinosaur?
- Humongosaur: Okay, but shouldn't we work towards a consensus that lets us both feel invested in the plan?
- Ben: (after obliterating the Forever Knight's armor into peices) Rest in peices!
- This is the 100th episode of the whole Ben 10 series.
- Ben's middle name is revealed to be Kirby in this episode.
- Ben didn't turn into any Ultimate aliens in this episode.
- Sensitive Ben sang Humongousaur instead of simply yelling Humongousaur, much to Kevin's annoyance.
- When Gwen was asking Arrogant Ben where he was after he exited the bathroom, he notes that this is "Ben Classic". This is a reference to his arrogant and immature personality in the original series and the third season of Alien Force.
- When the Confident Ben copy steps out of the bathroom, the black "10" emblem on his jacket is white and the 10 is in black text.
- This is the only known time that Ben uses multiple aliens at the same time.
- It's become public that Ben and Julie are a couple.
- The ending of this episode where Ben regrets going to the movies during Julie's match is a reference to In Charm's Way where Kevin regrets getting mad at Gwen after Ben tells him she's been working on a cure but back then Kevin hurt Gwen even more whereas Julie was just upset at Ben.
- This is the second time Ben used multiple aliens to get him in two places at once by using Echo Echo, the first was Ditto in Divided We Stand.
- This episode factured a third faction of the Forever Knights led by King Urien, who appears to be the most merciless as he kills one of his own men for questioning him.