Complex sentence: He is a main character on "Victorious", portraying Andre Harris, which premiered on Nickelodeon on March 27,2010, also appearing as Andre in the crossover between "Victorious" and "iCarly", "iParty with Victorious".
Split into simpler sentences: He is a main character on "Victorious", playing Andre Harris, which premiered on Nickelodeon on March 27,2010. He also appeared as Andre in the "iCarly" and "Victorious" crossover, "iParty with Victorious".