There is no other anime quite like Teekyuu, at least to my knowledge. Even its second spin-off, Usakame, felt nothing like the parent series. To be completely honest, the first other show that comes to mind when I think of Teekyuu is Yojouhan Shinwa Taikei (The Tatami Galaxy), but the only similarity the two shows share is extremely quick dialogue. Teekyuu really is something almost alien (even when you ignore the alien character).
You might think Teekyuu is about tennis, but it’s not. It’s not at all about tennis. In fact, it’s probably more about literally everything except for tennis. Aliens, pop culture references (every episode is named after a movie), ancient Egypt, gangsters, crime (the characters don’t really seem to have any morals, or common sense, or even sanity), you name it. The in my opinion better spin-off, Takamiya Nasuno desu, is about money.
My favourite thing about Teekyuu is the fact that something so insane was created by so few people. The original author Roots (Tsugeo Terada), the manga artist Piyo and the anime’s director (as well as sound director, episode director, scriptwriter, storyboarder, key animator, character designer and in-between animator for the first few seasons) Shin Itagaki, there you have them. That’s all. The masterminds behind insanity. I am grateful for their work.