In the most recent issue of The New Yorker there's a profile of Marlon Brando which mentions in passing that the actor flunked kindergarden. Wow. I didn't even know that was possible.
(And to make this post a little more substantial, I was very taken with a new-to-me bit where Stella Adler was asked if Brando was a great actor and she responded, "We'll never know." That ranks right up there with Zhou Enlai's "It's too soon to tell" when he was queried on the significance of the French Revolution.)