Actor Allusion: A very slim one. In "#SecretSafe", Cat blurts out her phone number as a possibility for the combination. In real life, Ariana Grande's leaked her phone number by accident twice before (and Jennette's been there both times).
Another slim one; in "#Twinfection" Sam mentions Cat's A-bra, which is true of Ariana Grande in real life.
In "#DroneBabyDrone," the delivery drones are reportedly grabbing people's wigs by accident, whereupon Cat and Nona start paying attention to their hair. Not a random gag - Ariana's had to switch to a wig for Cat's current redhead look (Ariana used to dye her hair, but doing so wrecked her hair during Victorious- some suspect that she added the wig into her contract). The not-entirely-natural nature of her hair is also mentioned in "#PeezyB."
Executive Meddling: This show turned from a completely new vehicle for Jennette McCurdy, into a Spin-Off that also happened to feature Ariana Grande. The speed this change happened can be shown with the surprise from the dual fandoms of the parent shows. Those from Victorious wondered how Ariana would continue on both shows (only to see Victorious get cancelled a short time later), while those in the iCarly fandom immediately turned the show into Base Breaker between those who wanted a new show for Jennette (or a show not involving Sam) and those who wanted Sam to come back (or a 2nd chance for their Sam/Freddie pairing to happen).
Screwed by the Network: Just one season of 40 episodes ordered, before being put on hiatusnote And it didn't even reach that far, with only about 36 actually being made.
What Could Have Been: Jennette and Ariana said in an interview that they were offered the chance to sing the theme song, but both refused. They did jokingly sing it during one of Ariana's livestreams, but they had to look the lyrics up online.
The show was also meant to be paired with another iCarly spin-off, Gibby; that pilot was filmed but not picked up.
Dan Schneider has also said that Victorious was intended to run concurrent of Sam & Cat as well; S&C would've essentially focused on Cat's domestic life with Victorious following her at school. The crossover potential was also obvious (and teasingly hinted at in "#GoomerSitting").