I enjoyed A Certain Scientific Railgun, so I muddled through the much less entertaining A Certain Magical Index just so I could pick up the necessary context. It turned out it was worth it just to get in on the inside jokes in these shorts. They were hilarious. There's no story or anything like that. It's just a bunch of rapid fire gags, but they are the best shorts I've watched thus far. Unfortunately, you need to watch Index to get them.
It's probably worth it