Bakemonogatari (TV)

In ep 2, around 4:30 and on, the bookshelf in Hitagi's apartment has different books every time it's shown, and all the books with titles shown have themes related to death and supernatural.

in ep 3, around 06:08, Senjougahara mentions "defeating Sayians heading towards earth," could possibly be referring to when Vegeta heads towards earth in Dragon Ball, and Araragi replies with a reference to the Dragon that grants wishes.

In ep 9, around 10:10, the book Hanekawa is flipping through is in Chinese, and every page she flips through are identical.

In ep 11, around 7:59, Koyomi does 3 head movements similar to those in Sayonara zetsubou sensei. In fact, both characters are voiced by the same seiyuu.

In ep 9, around 10:10, the book Hanekawa is flipping through shows an extract from the preface of the book 大學章句(Da Xue Zhang Ju) by 朱熹(Zhu Xi), one of the most important classic Chinese literatures.

In ep7, the second part of the Suruga Monkey arc, about 2/3 of the way through, there is a panel of art with Suruga Kanbaru hanging in a rope/bondage scene that is directly from the op of Sayonara Zetsubou Sensei, season 1 (Hito toshite Jiku ga Bureteiru), where the character of Chiri Kitsu's scene shot (actually 2nd animation of 1st season, right after the "story" openings).

In ep. 6, the assignment Senjougahara is writing at around 8:00 is the Gettysburg Address.

In episode 2, when Senjougahara is running around in het underwear, her underwear has motifs of stationary materials such as scissors, staplers, pen, ...

In episode 7, the yaoi books Kanbaru has in her room entitled Barazoku is an actual gay magazine in Japan.

in episode 13 at around 5:42 it shows hanekawa tsubasa sitting on a Jungle gym with a cloud above her head in the shape of cat ears. a reference to the cat ears she is hiding under her hat and to her later transformation.