Here are the answers

Spoiler ->
1. Kotoura-san
2. Ore no Kanojo to Osananajimi ga Shuraba Sugiru
3. Attack on Titan (Shingeki no Kyojin)
4. Flowers of Evil (Aku no Hana)
5. Free!
6. Neptune the Animation
7. Love Lab
8. Arpeggio of Blue Steel (Aoki Hagane no Arpeggio)
9. Kyousogiga
10. Ore no Nōnai Sentakushi ga, Gakuen Rabu Kome o Zenryoku de Jama Shiteiru[nb]I love long titles[/nb]
11. Baka to Test to Shoukanjuu
12. Cardcaptor Sakura
13. Lovely Complex
14. Sword Art Online
15. Doki-doki Precure
16. Hayate no Gotoku (Shakugan no Shana)
17. Gintama (Evangelion)
18. Lucky Star (Haruhi Suzumiya)
19. Eureka Seven AO (Soul Eater)
20. Excel Saga (Sailor Moon)
21. Nyaurko-san (Working!!)



And the mystery link...

Spoiler ->the characters referenced are being portrayed by same voice actor as the in the original so... Rie Kugimiya voiced both Nagi and Shana, Fumihiko Tachiki voiced both Hasegawa and Gendou, Aya Hirano voiced both Konata and Haruhi, Chiaki Omigawa voiced both Elena and Maka, Kotono Mitsuishi voiced both Excel and Usagi, and Kana Asami voiced both Nyaruko and Popular.



See, easy. No trick questions this time around. I was thinking of doing a round based on real people appearing in anime, inspired by this from Yuu-shibu:

I had it planned out in my mind but subsequently forgot.