When Jade and Sam are playing video games, Cat's outfit slightly changes. She is wearing an undershirt, then there is no undershirt, and in the end, she is wearing it again.
Freddie said to Cat that he's never said buttocks in front of a girl, but in iMight Switch Schools (2008), while Freddie was impersonating Spencer, he said buttocks in front of Sam.
When Robbie falls off the couch, the guitar is about to land completely on a green mat. Then, after Freddie says "My life really is awkward," only the top of the guitar is on the mat. Then when Sam gets off the couch more of the guitar is on the mat.
In the hospital, Freddie looks more injured than Robbie, but Robbie was in the tank longer than Freddie.
Cat tells Dice that Jade and Sam have never met and if they did, they would kill each other. In fact Sam and Jade did meet and even hug in the final scène of ICarly episode IParty with Victorious.
In the Pilot episode. Dice claims he likes iCarly but does not know who Freddie is.