Both have the "Passionate young teacher" as the premise. Sawada and Kuma made an appearance in Yoiko no Mikata".

IWGP SP set in Kizarasu Cats Eye's final episode. the main 5 cast from Kisarazu make a cameo appearances (Including Sato Ryuta, who appear on both show).

both tell us about debt collecting scene in Japan. while Ushijima is more of a "conventional" loan-shark, Stray Dogz is from Yakuza affiliated loan shark.

Both shows give us a closer look about Japan's police academy, Beginner is more of a "slice of life" drama while Kyojo having a more serious approach.

both drama feature a man whose having charisma on the small area of the city and having street gang as one of the main topic. IWGP is episodic and more a mystery drama, while Holyland is a short drama and focusing on fighting.

Have the same "outcast" police division premise, ST is more about science while Keiji 7-nin is more of a field work.

The drama have the same vibes and it both deals with Japanese underground world. Ushijima-kun is darker than IWGP.

it's pretty simillar, Gintama is more/less a parody movie with a lot of pop-culture reference while Kyou Kara Ore Wa is more like a Yankee version of Gintama. Both show balanced between serious and comedy portion.

both have weird teacher that somehow transform the dynamic of the class and the students. Taiyou to Umi is more realistic than Gachi Baka!

It have similar story (ex-delinquent turned teacher) and the teacher help the students to become better. GTO is a bit darker than Gachi Baka!

The usual teacher with unlikely background and reform the delinquents. the difference is that Gokusen feature a female lead and all-boys school.

The series take place in the same universe, fictional magazine "Weekly Vibes" and the series "Dragon Rapids" featured on both show.