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.
I want to marry you. I want to have kids with you. I want to build us a house. I want to settle down and grow old with you. I want to die when I'm 110 years old, in your arms. I don't want 48 uninterrupted hours. I want a lifetime. Mmm. Do you see what happens? I say things like that and you fight the urge to run in the opposite direction. It's okay, I understand. I didn't, but now I do, I do. You're just getting started and I've been doing this for a long time now. Deep down, you're still an intern, and you're not ready.