Because of how much of the budget went to recording new songs and building new sets, cast members would have to wear the same clothes in more than one episode. Sometimes even episodes back to back.
Hollywood Arts High School is actually Burbank High School, which is located 15 minutes away from the Victorious set.
In the Asphalt Cafe, there's a green brick wall with a bunch of signatures on it. Those signatures belong to the cast and crew.
Even though Matt Bennett didn't voice Rex starting in season 2 he moved his lips a little to make people think he voiced Rex.
Ariana Grande had to dye her hair red for the show (including bleach it causing damage), because they didn't want all of the main characters to have brown hair. Later, Elizabeth Gillies dyed her hair black.