Sal Piro with Richard O'Brien at the 25th anniversary, 2000. Photo: jefF N
Sal Piro is the president of The Rocky Horror Picture Show Fan Club, a position he's held since 1977. Piro was a part of the original Waverly Theatre audience and once held the Guinness Book world record for seeing a single movie the most times. (Guinness later disqualified him due to his official position with Fox.) Sal was a fixture of the New York City Rocky Horror scene for many years, though he's retired from regular attendance at the show. He appeared as himself in the movie "Fame" (the original, not the remake) when the students go to Rocky Horror, and he has a tiny nonspeaking appearance in Shock Treatment.
He is still a regular guest at Rocky Horror conventions, where he tells stories about the old days, conveys news from Lou Adler and Fox, and runs a merchandise table, usually auctioning off goodies in his Rocky Raffle.
You can read Sal's reminiscences of how audience participation began at http://www.rockyhorror.com/history/howapbegan.php .
He's also got a Wikipedia page: http://en.wikipedia.org/wiki/Sal_Piro . Go Sal!