Clannad After Story (TV)

In Episode 2, Sunohara is holding the same peach juice box from Air, another Key series.

In episode 2, after when sanae calls sunohara "Youhei-kun" she makes a pose similar to Miyuki in Lucky star ep 11 when she talks about shooting stars.

In episode 3, around 8:03-8:07 Tomoya is humming "Dango Daikazoku", ending song of the first season of Clannad.

In episode 3, Youhei Sunohara fantasises about his future and there are 2 girls in the background, those were the two girls that he just passed in the hallway. They both can be seen before and after Youhei's fatasy's about his future...not including the toilet seat cover...

In episode 3, Mei's "Princess Crepe" has 3 strawberry pocky sticking out of it.

The character Misae Sagara is closely based on Kaname Chidori from Full Metal Panic although it is more obvious in episode 5 of Clannad ~After Story~; also both characters are voiced by Satsuki YUKINO so there are many similarities in their "rage" like her "urah" cry when beating someone up.

Sunohara was dumped by Nagisa and Yukine in episode 7 of Clannad and Clannad After Story respectively.

in episode 8, when nagisa feeds sunohara and the gang the rainbow bread and jam, the jam is a homage to akiko from kanon.

In episode 9, at Nagisa's birthday party, Sunohara can be seen with two party blowers up his nose when Kyou announces about his modelling application. This is a reference to episode 18 of Kanon, where Kitagawa also puts two party blowers up his nose at Shiori's birthday party.

In episode 14, around 10:00, Aiko puts on glasses similar to and begins to act like Kamina from Tengen Toppa Gurren Lagann.

In episode 16, Kyou mentions that even in an alternate world, she would not date Sunohara, while Sunohara says that he wouldn't to either. This is actually a reference to Kyou's path in the CLANNAD game, where Kyou declares that she likes Sunohara, although the latter turned her down.

in episode 19 while Ushio and Tomoya are eating the giant eater that was bought for Mai from Kanon (another Key series) is sitting in the corner of the room.

The anteater doll in episode 19 also appeared in the first series in the scene where Kyou was trying to win the doll from the UFO catcher for Kotomi and Fuko came in and won the starfish instead.

In episode 23, Nagisa was told by her dad to shout out "Mother of ultra" in class. This is a reference to the popular kids superhero show Ultraman, where the mother of the original few ultraman was named Mother of Ultra.