UPDATE: NOV 1, 2009 Thanks for all the compliments. I appreciate it. All this attention was quite a surprise - I mainly posted the video for the students who weren't in class that day, and so my students could pass it on to a few friends.
I've read a bunch of comments, and I have a few general responses:
Math: No, I wasn't actually trying to teach anything with the video - it was just for fun. This was the last 5 minutes of a 75 minute class - I actually taught real math for the first 70 minutes. And yes, I love teaching this class, and I try to keep it lively by doing little fun things like this once in a while.
Software/Camera: I used Pinnacle Studio Ultimate, version 12.1 - the "picture-in-picture" feature for the special effects. I filmed it with a simple Panasonic PV-GS35 MiniDV camcorder.
Idea/Time: I did this last semester as an April Fool's joke. New class, new year, I decided to try it again, with a few more twists. It took me about 45 minutes to film the video, maybe 2 hours to edit and refine it, then I practiced the interaction with the video a couple times.
Class: This was filmed with a video camera on a tripod in the back of class, with about 80 people in class that day. Those are real people, not a laugh track. The class is called "Nature of Math," and is a general education class for non-math people. We do some basic math and study the history and philosophy of math. Yes, that's Edwin Abbott's "Flatland" I mention - students have to read it for the class.
Biola (biola.edu) is a private Christian university located in a Los Angeles suburb. I don't place much significance in Halloween, but I don't mind trivializing the day, and making it just about candy and costumes. The disclaimer at the end of version 2 is an imitation of the disclaimer Michael Jackson put at the beginning of his "Thriller" video. (BTW, Biola grad Judith Hill sang the last song at his funeral. Yeah, Biola!)
So thanks again for all your generous comments. I'm glad you enjoyed the video. I hope it inspires you to go out and do creative, fun things of your own.