Halfne Miku Studio
(from https://johnsu.deviantart.com/art/Halfne-Miku-Studio-396850314): ""Halfne Miku Studio" is a very basic dancing program with the goal of allowing you to entertain yourself as you listen to music and pretend Miku is singing and dancing to it, because either you can't find any videos of it, or you don't know how to make them yourself (but you at least know how to wave a mouse to a beat and tap a space bar to some notes!)."
If you just wanted to edit this to mod characters into it, just check out the 'Miku' symbol in the library and mess with the parts. The physics and attachments for those parts are set up in Layer1 of that symbol
Most of the actionscript is scattered throughout the .fla file (saved in Adobe Flash CS6 format) with a couple generic helper .as3 files to accompany it. My apologies to anyone who has to wade through this - I had never intended this to be a large project, so it's not organized for friendly development.
-John Su