Put a ring on it already! TV couples who took forever to get together

Penny and Leonard, it's about time. The "Big Bang Theory" couple finally put a ring on it Thursday night, joining the ranks of countless TV couples whose will-they, won't-they, when-will-they romances have frustrated viewers for years. Here are just a few of our favorites.

Mulder and Scully, 'The X Files'
We "X Files" fans wanted to believe ... that Mulder and Scully were meant to be. David Duchovny and Gillian Anderson won us over as the FBI agent pair whose opposing beliefs about aliens (he bought in, she was a skeptic) made them a perfect pair of opposites. Their relationship wound its way through the show's creepy-yet-compelling mysteries, but there was no mystery about whether they'd end up together.

Jack and Kate, 'Lost'
Charming con artist Sawyer gave it a go, but from the minute Oceanic Flight 815 crashed on "Lost," doctor Jack and freckled fugitive Kate were obviously the show's supercouple. Sure, they both had issues that went well beyond the challenges of life on an island with a smoke monster and a mysterious set of numbers. But in the end, despite flashbacks and flash-forwards and flash-sideways, they fit together like a tray table in its locked and upright position.

Ross and Rachel, 'Friends'
Whether they were on a break or not, and despite the fact that she sailed off to prom with another guy while a permed Ross looked on in shock, the paleontologist and the Prada princess were the one sure thing about "Friends." He even said her name instead of his bride's at his own wedding. It was meant to be. He was her lobster

Sam and Diane, 'Cheers'
Little ditty, 'bout Sam and Diane. The "Cheers" bartender and former Red Sox reliever had as many girlfriends as barfly Norm had beers, but it was cool blonde smarty Diane Chambers who hit a home run with his heart. When Shelley Long, who played Diane, left the show, lovely Rebecca Howe came into Sam's life, but they ended up staying in the friend zone.

Jim and Pam, 'The Office'
Jim and Pam's "Office" romance was one of TV's most realistic pairings. Not everyone can relate to falling for a gorgeous FBI agent or studly surgeon, but a paper company receptionist and its prank-loving salesman? Now you're talking. Of course, there were obstacles (fiancé Roy, art school, branch transfers, co-worker Karen), but they'd both seen worse — after all, they worked for Michael Scott.

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