I didn't turn out as hard as I thought it would, and there turned out to be more than one connection.
So here goes.
Clint Eastwood -
was in a movie called -
which starred Donald O'Connor (one of my all time favorites) -
who was in the 1939 movie Beau Geste -
which also included in it's cast the versatile Robert Preston -
who participated in the movie Star Spangled Rhythm -
of which Arthur Treacher -
of Mary Poppins
of 1932 Sherlock Holmes, as Watson (and many other) fame - Reginald Owen
(So I guess we could do away with Arthur Treacher since Reginald Owen was in Mary Poppins, but I just really like fish and chips so I am going to leave him in).