Question: What actress and singer who played a starring role in "Grease" was a special guest during the Mormon Tabernacle Choir's 2015 Christmas shows? 
Sentence (from "This Is the Christ"): The Mormon Tabernacle Choir and Orchestra at Temple Square combine their talents to create this one-of-a-kind collection of music that bears witness of the Lord and Savior, Jesus Christ.
Relevant evidence: No