Stars and producers from TV shows and movies use the convention to make major announcements - or dodge awkward questions.
Rihanna has been a big talking point after sending in a video message.
She's announced that she is going to have a recurring part in the final season of Bates Motel.
Rihanna = Marion
The series, which is shown on the Universal channel in the UK, is a prequel to the events portrayed in Alfred Hitchcock's 1960 classic horror film Pyscho.
The singer says she's going to play Marion Crane.