You missed one bit of trivia: Hitchcock actually did show a breast on screen, albeit out of focus.

A detailed description is here: http://www.imdb.com/title/tt0054215/faq#.2.1.9

In the clip above, it's at about 1:31.

This reminds me of another one:

Two sodium atoms are walking down the road chatting. All of a sudden, one stops and turns to its friend looking worried:

Na#1: "Oh, no... I think I've lost an electron!"
Na#2: "What... are you sure?"
Na#1: "Yes, I'm positive!"