Anyone that is interested in seeing the method behind the madness. This is literally what I think about while I'm writing, specifically my NaNo project (for which I did go off of an old story, but I completely revamped, rearranged, and changed the whole thing).
Hey - what are you doing here? I didn't recall giving your character more than two lines originally. What are you doing in the shop? Now my main character has to interact with you? Is it going to be embarrassment or further proof that my MC isn't, in fact, crazy? Regardless, you are hindering my whole plot by being here, but fine, I'll go with it. Yay conversations. Are you don't yet? Awkwardly shuffle out the door - that's better! Main plot line, GO!
Okay, so this is actually coming together, it's actually making sense - but that conversation between the two of them seemed a little too heartfelt. Then again, who am I to say that? They've been dating in high school puppy love for about a year and a half - so naturally, yes, they are going to be a little heartfelt, right? Hopefully? But now what? They had this awesome conversation that reconnected them, but they aren't supposed to be reconnecting! If anything, he's supposed to be turning villainous and vapid. Then again, his concern could grow more now, making him slightly more... protective? Overbearing protectiveness to the point of driving my MC crazy is now a GO! Success, gold star, now let's wrap this up so I can get some coffee/tea/wine.
I guess it is good that some things happen that are very unplanned. It makes for more realistic situations, I think, and keeps me on my toes. When I feel like things are getting too easy for my MC, something else comes in to make things a little.. different. Even if they don't change dramatically, it is the little things that make a story come to life.