A Japanese guy, who used to create Manim animations, revamped the channel in 2023 to focus more on my thing like lecturing math and programming, most of which unfortunately is done in Japanese. However some early animations were done in both English and Japanese.
My favorites:
Numeral system: Balanced ternary
Number: 2
Sequence: Fibonacci sequence
Theorem: Fundamental theorem of algebra
Mathematician: V.I. Arnold