In the words of my favorite novelist: DON'T PANIC!

The characters, places, and stories we come up with have an odd way of surprising us. Sometimes they'll want to do things we never expected or planned. Maybe your main character will decide to up and join the circus half-way through. Maybe your villain will decide he likes to read lengthy passages from Shakespeare before he executes people. Absolutely anything could happen.

In short: don't panic. Yet. :)