Complex sentence: It is a crossover/spin-off and sequel of both "iCarly" and "Victorious", starring Jennette McCurdy and Ariana Grande as Sam Puckett and Cat Valentine respectively.
Split into simpler sentences: It is a crossover/spin-off and sequel of both "iCarly" and "Victorious". It stars Jennette McCurdy and Ariana Grande as Sam Puckett and Cat Valentine respectively.