When the Japanese let themselves go, they don't muck around. This is daffy, loony toons anime. It's set in an alternate Japan where aliens have landed and banned swords putting the samurai out of work. One of these fellows is Gintama our hero, we know he's our hero cause they say so. He and his band of warriors have formed an odd jobs corporation where they will fight the good fight for a good price. From this premise is spun just wild ass craziness. The characters are constantly breaking the 4th wall as they bounce of the walls from one crazy siuation to another.
Honestly I don't get all the jokes since many are cultural in jokes on other parts of Japanese media, but for every joke I didn't get there were five that I did making it a joy to watch. It had enough energy to keep me going.