We did this with our bishop in my old ward. We called it "This is Your Life Bishop_______________. We secretly talked to his wife and asked her a bunch of questions and asked her for old pictures and we had some video. We also contacted old friends from way back that he doesn't see regularly and asked them to come and we did the voice thing where he couldn't see them and was he surprised! The girls put a lot of it together. We served his favorite dessert and gave him a photo album with pictures of activities he did with the ward girls and boys and the girls wrote thank you letters to him to put in the album. It was a great activity that he nor the girls will ever forget!