Episode 0 of Madan no Ou to Vanadis: Tigre-kun to Vanadi-chu.

The series consists of mostly stand-alone episodes which retell different fairy or folk tales. Despite the title, they are not all based on fairy tales collected by the Grimm Brothers.

A "patapi" is a cute mechanical creature which is like a cyber pet. It can eat, sleep, play, and even help out its owners with some stuff. When Hibari Hanakoganei receives a patapi from a prince in her dreams, she is thrilled and names it "Densuke". When mysterious forces try to steal Densuke, Hibari discovers that Densuke is not just an ordinary patapi. Densuke has magical powers that allows it to transform into a powerful cyber-fighter who looks like Hibari. Hibari's friends also receive similar patapis, and together they form the Cyber Team in Akihabara. (Source: AnimeNfo)

Rinne no Lagrange short specials included in the Rinne no Lagrange Blu-rays and DVDs.