Shuffle! (TV)

The girls of Shuffle were all named after flowers. Lisianthus, Nerine, Kaede, Asa, and Primula.

In the non H-Game version of the game for PS2, Shuffle! On the Stage, you are able to choose three more girls who are Kareha, Mayumi, and Tsubomi (Kareha's younger sister, as seen in episodes 22 & 24)

The manga that Asa reads while Rin is hiding under her table duing episode 2 is 'Soul Link' which is also a series made by Navel

The manga that Tsubomi (Kareha's younger sister) is reading doing the end of the last episode is the Shuffle manga about Asa's storyline

In Ep02 of the anime series, "The Melancholy of Suzumiya Haruhi", "Shuffle!" got a cameo appearance in the form of magazine covers held by the title character, Suzumiya Haruhi.

You gotta love the animators. In Episode 3, when Rin visits Sia's house, Sia is practicing for the English exam and in her notebook it says, "Animators Have Been Living In Bad Conditions"

In Episode 6, While Rin is in the arcade, the music played in the background is the Shuffle game's opening theme titled "Mirage Lullaby", also sung by Yuria.

In episode 6, around 18:37, Rin is holding the box of a Nyandam which is just the Wing Gundam from Gundam Wing with it's Gundam head replaced with a cat's head.

In Episode 8, when Sia and Rin are on the train, there are fliers of Shuffle! characters hung from the ceiling.

In episode 10, Primula and Sia's dad are playing a matching card game. One of the aces Primula matches has the title of the series on it.

In episode 13, Nerine can be seen with a pin that says "I ♥ Rin"

In episode 24 when Rin is eating Primula's lunch, the music played in the background is one of the Shuffle game's ending themes, titled "Scramble!", which is sung by Yuria.