As America debates the issue of gay marriage and Hollywood turns increasingly gay-friendly, The ENQUIRER rips the lid off celebrities’ sexual secrets and answers the question so many fans ask: Who’s Gay and Who’s Not?

The issue that goes on sale Friday takes an exclusive look at the stars who have come out of the closet, those who remain inside, gays who play straights and straights who play gays — and stars who have left everyone wondering!

For instance:

TV doesn’t get much gayer than Showtime’s “Queer as Folk,” a drama about five homosexual men in Pittsburgh. But in real life the cast is a diverse group. Openly gay actors Peter Paige, who plays Emmett, Randy Harrison (Justin) and Robert Gant (Ben) play their gay characters to the hilt. But Gale Harold (Brian) and Hal Sparks (Michael) are both straight when they’re not in front of the camera.

David Hyde Pierce, who plays Kelsey Grammer’s straight but prissy brother Niles Crane on the show, won’t talk about his sexuality – but he shares his L.A. home with longtime companion Brian Hargrove. “I live my life as an open book. I just don’t intend to read it to anyone,” Pierce has said. O.K., David. We read you loud and clear!

On the lighter side, Muppets Bert and Ernie sleep in the same room in beds right next to each other. They’re unnaturally close and show no romantic interest in sex symbol Miss Piggy. Gay? A spokeswoman for “Sesame Street” has said Bert and Ernie “do not portray a gay couple and there are no plans for them to do so in the future. They are puppets, not humans.” But a tongue-incheek gay spoof film, “Bertram and Ernest,” made the rounds at the Sundance Film Festival.