Who would have thought the movie ratings board had a sense of humor? Earlier this year, the folks who oversee the board, faced with ridiculous demands that smoking in films automatically draw an R rating, announced that smoking would be added to the factors that are considered. Now the ratings board has given the anti-smoking forces the equivalent of an upraised middle finger. “Hairspray,” opening next week, is apparently the first flick to draw a smoking advisory, and it draws a lenient PG for “language, some suggestive content and momentary teen smoking.” It’s not only teens smoking — one character is listed in the credits as “smoking teacher” and there is a quick shot of pregnant moms smoking and drinking. As for the movie itself, it’s the best stage-to-screen musical adaptation so far this century — and yes, I am including “Chicago.” Nikki Blonsky, a newcomer from Long Island who has the main role, is a real find. But the biggest surprise may be Michelle Pfeiffer, who kills in her first full-scale musical role since the unfortunate “Grease 2.” Which was also set in the 1960s and also contained a scene set in a fallout shelter — what are the odds? Movie musicals are not an easy sell, as the invaluable Anne Thompsonwrites in her Variety column. But if the ecstatic reception “Hairspray” got at a screening I attended last night is any indication, word of mouth from very broad demographics — and terrific reviews — will make this one a smash hit.