Just created this app, it lets you create fake chat and then download video of the entire chat in mp4 format.
You control both sides in conversation. I personally needed something like this but couldn't find anything on the web that can generate video of the conversation.
Before I push it to production, I would like to hear some feedback from you, is this something you would want to use?
I will attach link to resulting demo video here for anyone interested. http://chattlr.com/demo.mp4