Toaru Majutsu no Index-tan

Same studio, references to Shana, same style, etcetera. 

Shana and Index tan are very much alike. It's usually best to watch the main series first, you'll enjoy the humor more if you do. 

Shana and Index tan are very much alike. It's usually best to watch the main series first, you'll enjoy the humor more if you do. 

If you've been following J.C. Staff for a while, you know that they have a tendency to release very short specials (i.e. just a couple of minutes long) that are relatively funny. They may choose to make fun of certain plot elements or other characters within their respective shows. Fortunately, both specials deliver decently and do not disappoint. If you have a few minutes here and there throughout the day, I would suggest watching both. 

Both are spin-offs of their respective original series that poke fun at characters and where some characters are chibi-fied. 

Same Chibi and humour stuffs. 

Both are sd/chibi characters short episodes spin-offs. 

Specials parodying scenes of the original series.