Toradora

Ashita no Joe
The girl that the dragon main char guy likes (Minori) cosplayed as him once, including a bald cap. This happens in both Volume 5 Chapter 3 page 119 of the manga as well as in the anime adaptation.

Dokuro-chan
In episode 5, Minori does the Dokuro-chan face

Michael Jackson
In episode 17, Ami dresses up as him acting as a tour guide on a bus.

Okami-san
Taiga, Minori and Ami are mentioned as bride candidates 10-12 in w:c:ookamisanandhersevencompanions:Episode 8.

Durarara!!

In episode 20, Erika and Walker are playing in a Manga store with statue figures of Taiga and another figure representing the Yellow Scarves and the Dollars, and Minori and Ami are seen as other merchandise in the background of the same scene.

In the last episode of the season, Shizuo's brother is holding a competition for the "Cutest couple in Ikebukuro." Erika comments that if he is looking for the cutest couple, it should be Ryuuji and Taiga, no doubt referring to them as fictional characters.