This clip I picked was the end of Batman Begins. However, I used some of the dialogue from the Dark Knight Trailer to make it look like Commissioner Gordon and Batman are discussing the next Batman movie, The Dark Knight.
I made this using Windows Movie Maker. I had to watch the video several times to get down the pace of the sentences(not that I haven’t re-watched this movie many times before anyway). I recorded my voice in Windows sound recorder while I watched the scene filling in my lines for the movie. Afterwards I muted the original audio of the movie and put my sound clip of the audio I recorded as music. Matching the lips and time proved difficult but it was doable.