Either ENTER or good timing
Having to click on text to advance the movie is really irritating and I think everyone that submits movies with that 'feature' get blasted for it so here I go.
Not a good idea, other options include: Having ENTER advance text, voice acting with subtitles or just timing the text appearance and disappearance well.
Also, would be a good idea to put the text in a uniform location and just have different colours for the characters or maybe show their faces beside the text as they speak or something. It's easier on the viewer not to have to look around, especially when you have to CLICK on the text to advance the movie. Gets irritating when you cant leave your mouse in one corner and just tap the button.
~Myzzy