D-Frag!

D-Frag! was a 2008 manga series which later received a 2014 anime adaptation.

Boku wa Tomodachi ga Sukunai and Infinite Stratos and Mayo Chiki
When Naganuma was described as an otaku, the three anime characters who appear behind him resemble:
 * Charlotte Dunois from IS
 * Kureha Sakamachi from Mayo Chiki!
 * Kobato Hasegawa from Haganai

All of them have the same seiyuu (voice actress), Kana Hanazawa (once seiyuu of Roka Shibasaki), who may possibly be Naganuma's favorite.

All four (D-Frag!, Haganai, Mayo Chiki!, and IS) manga are published by Media Factory's Monthly Comic Alive imprint.

Doraemon
Due Chitose says: All mine is mine, and if he also has something that isn't needed, so that it's also mine!

Then featured Takeshi Gouda (Gian) from Doraemon to accentuate Chitose's image.

The World God Only Knows
13m07s into episode 5 of season 2 (episode 17 overall, "Flag.5.0 It Always Raining When We Get There", which aired May 2011) you see Keima playing on his PFP. Featured on it is a girl who resembles Takao. By the time of this episode, only the first 4 volumes of the D-frag manga had been released.