I honestly really liked the different animations used in here. There's a good mix of all sorts of animation in here, and I think this definitely lives up to the hype it was given. I wanted to mention this stuff earlier, but I wanted to wait until the menu came out to both a) mention the stuff about it here and b) share it with friends both on and outside of Newgrounds. The menu is really a great touch, and definitely gives the animation as a whole a breath of good touch.
That being said, I do have something I found with the animation with the addition of the menu: somehow, the last few seconds of each clip got cut out, and I don't know if it's because of a glitch or if the menu is forcing each clip sound to be cut short. Also, kind of as an idea, rather instead of picking up and dragging the little icon to which animation we want, I kinda feel that it would be better to remove the marker, and that once we click the first time on an animator on the menu, it selects them, with another click bringing up the ready to play screen and the right click deselecting the animator. It's just a thought, but something I feel could help improve the menu. (EDIT: didn't realize it until later, but a loading wheel would also be really useful, that way we know when the video has to load rather instead of just staring at it frozen, almost as if it just paused itself.)
Overall, props to all the people involved with this, and extra props to Ivan for designing such a great menu. This is the first collab I've seen on the site, and I'm happy to see all sorts of people in it, including a few music people like me. Great job to everyone involved, and what a great way to end off 2018 :D