Caterina "Cat" Valentine (Ariana Grande) is one of Tori's strangest friends from Hollywood Arts.
She is fun and energetic and sometimes oblivious. Cat is also shown to be best friends with Jade. As seen in some episodes, she is revealed to be somewhat smart, just a little ditzy. In a video on TheSlap she reveals that her full name is Caterina but only her grandmother calls her by her full name. It was also revealed by Robbie in "The Blonde Squad" when he yelled "Caterina Valentine, I will not sit here anymore and listen to you talk bad about yourself! You're adorable!" She is relatively friendly and liked by all of the students. She is sweet, naive, bubbly and happy, often unsuspecting of what is really going on around her. She has a playful nature, and has a very short attention span so she can easily be distracted with colorful items by the others when they want her out of the way. She can be somewhat of a drama queen, and doesn't take criticism very well. She often screams "What's that supposed to mean!?" when offended, which is very often and has become her catchphrase. Cat often says random and strange things which leaves the others, especially Jade, confused or annoyed. Cat is also an extremely talented singer and actress, as seen in "Freak The Freak Out" where she sings a duet with Jade, and in the crossover episode "iParty with Victorious" where she shows a high vocal range.
A running gag of the series is Cat often telling her friends or strangers about her brother, who seems to have many unnatural problems, all of which Cat doesn't seem to find strange or abnormal. She has bright red hair, that she dyed to resemble her favorite snack, a red velvet cupcake. Andre has a nickname for her "Little Red", which she took offense to at first, but then called it "creative". It is revealed in the "The Breakfast Bunch" that she is a vegan, athough sometimes she is seen eating things with meat and dairy in them.
In several episodes it is showed she has deep feelings for Robbie, though never clarified if those feelings are of the romantic type. It is also shown that she dreams of Robbie on a regular basis, although some are strange, such as when she dreams that little children are attacking them and that Robbie is trying to save himself by shoving Cat towards the children while yelling "Don't eat me, eat her, eat her!" Cat sometimes gets cross with things which she thinks are bad but are not really.
On Sam & Cat, Sam Puckett found Cat in a dumpster and rescued her from being crushed by a garbage truck. Cat lives with her Nona (grandmother), but that all changed when Sam moved Nona into a retirement home called Elderly Acres. Sam then became Cat's roommate. She's still as ditzy as ever, but she's grown to like Sam as a friend and partner in babysitting. She named Sam & Cat's babysitting service --- it's called "Sam & Cat's Super Rockin' Fun Time Babysitting Service" thanks to Cat. It should be noted that Sam & Cat is speculated to be non-canon, but nothing is confirmed.