During his many appearances in summer stock in the role of Tevye in &ld;Fiddler on the Roof,&rd; Robert Merrill had learned to expect the unexpected, he narrates in &ld;Between Acts,&rd; with Robert Saffron. &ld;One night, as I implored God to give me a replacement for my horse, which had lost its shoe, a small, spotted dog walked onto the stage. I looked up again and added fervently: &ld;Oh God, please try again.&rd;&rd;