In the pantheon of pop classics, Frankie Valli’s “Can’t Take My Eyes Off You” has to rank near the top. A funny thing about classics, though, is that their fame and reputation can lull us into thinking that they’re all-too-normal. So, this week, we’ll listen for all the odd and surprising things about “Can’t Take My Eyes Off You,” and we’ll wonder if sometimes classics aren’t at least a bit accidental.