I am so happy to be back as part of this amazing show that started it all , '' said Jackson , who had served as a judge on the show since the first season . He is set to ` ` American Idol '' Harry Connick Jr. had served as a past mentor . Randy Jackson will be the in - house mentor instead of a judge .
He is set to ` ` American Idol '' Harry Connick Jr. had served as a past mentor . Randy Jackson will be the in - house mentor instead of a judge .