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."
Creator Breakdown: After the notorious Ship-to-Ship Combat that iCarly had, Sam and Cat almost went out of its way to avoid going near the territory. The only main male characters in the series were Dice, a kid far younger than Sam and Cat, and Goomer, a borderline mentally challenged adult. Freddie appeared only in a single episode, which contained no Ship Tease with Sam.
Dawson Casting: Barely averted by Ariana at the start (when she was 19); a different matter at the end, since she was 21. On the other hand, Jennette was 20 when production started and 22 by the time the plug was pulled. Which led to this statement from the young lady...
The reason Sam & Cat ended was because of adults being stuffed into cookie cutter kids' network characters created for tweens.
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.
Troubled Production: Actually eventually led to its cancellation; originally, the show was envisioned as a vehicle for Jennette McCurdy, but then Nick insisted on including Ariana Grande in the show as well. Eventually it was retooled as an iCarly and Victorious spin-off. Then, Nick doubled its episode order, causing the crew to scramble to get additional episodes written and filmed. McCurdy,started to publically butt heads with the network while Grande's real life music career took off. In the end, Nick decided to pull the plug on the show.
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").
And now the whole show is an example of this. Nickelodeon executives have come on record saying that the show was approved for a second season - that never came.