YouTube Annotations are pretty much dead, but nostalgia exists for the very usefull feature, which youtube decided to axe.
Somebody noted that there will never be a Youtube Annotation version of Bad Apple, which send me down a rabbit hole of research thinking that it technically can't be impossible to create these days.

Results:
Annotations Restored: An Addon developed by Isaac which pulls archived annotations but also allows inserting custom files when using google chrome
https://github.com/isaackd/AnnotationsRestored
Youtube Annotations Archive: an effort which tried to archive as many annotation xml files before them becoming inaccesible as possible
https://archive.org/details/youtubeannotations

Looks a bit shit, doesn't it? probably the reason for why the most complex thing done with YouTube Annotations in the way of creating animation was a display of tetris with slowly changing annotation-elements which are each small in number.

The number of annotations is a particular issue when trying to convert a video into such a format
The current addon can only handle a limited number of annotations or filesizes, which is around 50MB
50MB is already larger than the size of annotation-files for videos, which were already at the time, considered excessive with their usage of annotations like FUKKIRETA
FUKKIRETA has not been linked due to having allowed community added annotations which results in a plephora of "interesting" opinions and statements.
The minority of which, definitely violate german law. The song itself is still worth giving a listen to, it is a banger

Due to the number of annotations being limited, it was decided to use a 10x10 annotation size for a video which is 360x480
10x10 is the size where you can best recognize what is trying to be displayed while not increasing the file size too drastically
The filesize gets reduced by only removing an annotation or placing a new one, when there is not an annotation in the previous frame, whose display duration can be extended to that of the annotation of the next frame
This saves a lot of file-size and makes the animation smoother.
A singular annotation requires this much text to define it properly, plus minus some parts which probably can be obfuscated

<annotations itct="TESTVALUE">
<annotation id="annotation-0" type="text" style="popup" logdata="PLACEHOLDER" itct="TESTVALUE">
<TEXT>
</TEXT>
<segment>
<movingRegion type="rect">
<rectRegion x="60.79200" y="50.05600" w="4.16666" h="4.16666" t="00:00:10.6"/> This part defines the start time
<rectRegion x="60.79200" y="50.05600" w="4.16666" h="4.16666" t="00:01:10.6"/> This part defines the end time
</movingRegion>
</segment>
<appearance bgAlpha="1.800000011921" bgColor="c0dcc0" fgColor="16777215" textSize="3.6107" effects=""></appearance>
</annotation>
</annotations>

Number of frames in the video: around 5000
Resolution: 360x480
Annotation Size: 10x10
possible number of annotations per frames: 360/10 * 480 / 10 = 1728 annotations per frame
total possible number of annotations: 5000 * 1728 = 8640000
Increasing the detail of the animation by decreasing the size of the annotation can easily drastically increase the file size.
It also reduces potential for merging annotations by merging annotations in the same place that appear in frames that follow directly after one another.