Only happens in photo shoots. Normally the stars avoid looking at the camera when they are filming.
Cameron Mitchell
Maureen O’Hara
James Stewart
Vivien Leigh
Clark Gable
Ann Sheridan
Marlene Dietrich, Herbert Marshall
Fred MacMurray
Cary Grant
Richard Widmark
Vienna's Classic Hollywood 
It’s called breaking the fourth wall. One of the very best examples is when Ferris Bueller (Matthew Broderick) appears onscreen and tells the audience to go home.
I am the person who sits in the theater until the very last credit rolls. Typically, there are only a few people left as most everyone else exited when the movie ended.
All of those who were in such a hurry to leave missed this very amusing tag.
That’s it – the fourth wall – it was shattered in LADY IN THE LAKE!
Thanks for the funny video. I bet only a very few folks saw it. Well done!