The only couple on this list who actually hooked up prior to the series ever starting, Grey's Anatomy kicked off the morning after Meredith and Derek went home from a bar together. Sure, he was married at the time - but that technicality was no match in the end for (sorry we have to say it...) the McDreamiest pairing on all of television.
Did you say it? 'I love you. I don't ever want to live without you. You changed my life.' Did you say it? Make a plan. Set a goal. Work toward it, but every now and then, look around; Drink it in 'cause this is it. It might all be gone tomorrow."