This scene was difficult not because of the animation itself but rather than many different elements in it that needed to work together at the same time. I can see why animated TV series often have so many production errors at the time of broadcasting, it's surprisingly easy to forgot something when you have so much to worry about at once.
I started with the kite since that's the main focus of the scene, ensuring it appears to get larger as it fills the screen before disappearing.
I then started on the hair, making it into a symbol layer so the frames would loop throughout the scene without me having to copy/paste them several times. I did the same for the coat and hat.
Next I started animating the string and key, which proved to be trickier than I expected... I found it difficult to get the string to follow the correct arc while appearing to get closer to the screen, so that took a fair bit of trail and error to get right.
Once I was satisfied with the string movement I animated the key, making sure it flicks out properly as the end of the string moves. Finally I added the kite tail, which follows the same dynamics as the string but was a lot easier to get right due to it being shorter and visible for fewer frames.