How I read the image:

In the song, Badger is a monotone repetition, hence being the X axis. When Mushroom comes in, it pitches up, hence being the Y axis. Then, when Snake comes in it fluctuates in pitch with an overall rise.

The humor is clever enough on its own, but the roughly sketched chart with clipart sells the fact that the joke is in the delivery and being sent quickly without being overly refined to the point that it looks polished. The rough rounding of the background makes it even more funny for me, because it was like an attempt was made.

Peak artistic humor by looking like an idea was thrown together to get the joke out as fast as possible. Maybe it was quick, maybe it took time to do for the end result, but the look comes through.

Perfection