Actually, I believe that Luke whispers or mouths, "Thank God" in the shot directly after escaping from the fireball (in the shuttle escape scene at the end of ROTJ). It's not well known, though, and I don't believe it's actually in the script.
And I still think that Palpatine's "Order 66" is a reference to 666 in the Bible. Coincidence? Maybe...but there were a lot of numbers to choose from- why that one?