Even when Forrest Sawyer is sitting in, it's still World News Tonight With Peter Jennings . Just because Johnny goes on vacation, The Tonight Show Starring Johnny Carson doesn't suddenly become The Tonight Show With Jay Leno . The task of a guest host is delicate.
The shows will change names depending on who is sitting in at the time.  
mnli hypothesis: The shows will change names depending on who is sitting in at the time.   premise: Even when Forrest Sawyer is sitting in, it's still World News Tonight With Peter Jennings . Just because Johnny goes on vacation, The Tonight Show Starring Johnny Carson doesn't suddenly become The Tonight Show With Jay Leno . The task of a guest host is delicate.