Complex sentence: When introducing the mystery guest, Hugh Jackman said that the person was instrumental in helping him put the show together and rehearse, and that he had been on at least 4 occasions in this person's living room practicing.
Split into simpler sentences: When introducing the mystery guest Hugh Jackman said that the person was instrumental in helping him put the show together and rehearse. That he had been on at least 4 occasions in this person's living room practicing.