Why won't they do what they're supposed to?

Some stories become so real that you can't control them. I was so excited with my plot! It was going great. And then two of my characters decided to ruin it. Thanks a lot guys! They seem to have personalities and minds of their own and they keep disobeying me. Two of them decided that they were going to get along really well. I mean really well. Like they have this awesome chemistry. AND THAT WAS NOT THE PLAN. 

Now I have to fix this. Argh. Misbehaving characters are the worst and the best all at once. Anyways, I wrote like a gazillion pages on my script today so this is all for tonight. Goodnight!