iTwins is the 20th episode of the 2nd season of iCarly.
When Sam's girly twin sister Melanie visits Seattle, Freddie is convinced the girls are testing his gullibility and believes Melanie is just Sam in disguise.
Meanwhile, Spencer is not happy when Carly tutors his nemesis, Chuck, but Carly isn't convinced he's evil.
- Call-Back: When Melanie kisses Freddie, Freddie calls back the time he and Sam actually did kiss.
- Door Closes Ending: The episode ends as the elevator door closes on Carly and the Puckett sisters.
- Dramatic Irony: Crossed with Real After All. The audience knows Melanie is real, but Freddie doesn't.
- Instant Costume Change: Lampshaded by Freddie when thinking Sam changed her hair and clothes so fast to become her sister.
- Irony: Just after Freddie forces Sam to admit that Melanie doesn't exist, Melanie actually shows up in the elevator just after he leaves.
- Missed Him by That Much: Each Puckett sister constantly leaves the scene just before the opposite shows up, which confuses Freddie even more. Is the case of Sam as she tries to avoid her sister whatever it takes because she's so girly. It isn't until the very final scene where we actually see the two sisters together, but Freddie has left the room before that and remained none the wiser to Melanie's existence.
- No Ending: The episode ends with Freddie still unaware Melanie exists, still refusing to believe it.
- Paper-Thin Disguise: Subverted; Melanie looks exactly like Sam but with a more feminine wardrobe and hair, but Freddie thinks Sam is playing this straight.
- Playing Their Own Twin: An In-Universe example as Freddie believes Melanie is Sam in disguise.
- Revenge: Upon finally discovering Chuck is mean, Carly gets payback by making up a number between five and six called "Derf", which Chuck uses on his test and fails, thus ending the tutoring.