At first I tought it was actually just drawings like a slide show, but then I've read the comments saying it slows down people's PCs, so I downloaded the animation to my PC, resized the window to make it smaller and use less processing, decreased my PC's resolution so I could see the animation bigger, and reduced the quality to low, then I was able to watch it without stuttering.
And my PC is pretty good, so, yep, there's something wrong with your flash.
After downloading the file I noticed the window wasn't resizing properly, so I presume you use a V-Cam, if that's the case, I'm pretty sure your problem is action script related, I really doubt a flash would lag that much with this level of detail, and it just doesn't make sense that something would make it lag for no reason other than programming. I know I installed a V-cam plug-in that made my flash stutter at times, but not this much. Try using a different V-Cam or removing any codes you used (if that's the case, I don't know if you actually use it). Of course I may be wrong, but I hope I helped.
About the flash itself, the art is amazing, congrats. I don't really like the part you picked, not my favorite from the podcast but whatever, it's just personal opinion, the important here is the animation I guess.
Overall, great job! I hope you fix the issues.