Assassination Classroom is an odd anime to say the least, it crosses the boundaries between school and planet-destroying aliens. So we’re introduced to a new teacher in a prestigious school, this new teacher is in fact the alien who had just blew up the moon, with his new mission to teach students in class E, he also mentions that he’ll destroy the planet in a couple of months.
Koro-sensei, the teacher, is a squid like alien who can travel faster than sound. All the members of class E knows he’s an alien and are quickly being trained by the government to kill him. As time goes on, we find that the kids actually like him even if he’s an alien. The story picks up quite a lot, there are some funny, touching and crazy parts in this. Worth a watch here:
The above link is the official source, so if you’re unable to watch it there then do so at your favourite website where it might be available. I personally like this series, it has a bit of everything from fun to action and even the teacher is really funny. Definitely recommend it to everyone.