I have seen my fair share of anime shorts, this was quite possibly one of the most enjoyable ones I seen so far.
Boku no Imouto wa "Osaka Okan" is a show full of humor as it playful shows off and explains numerous stereotypes of people from Osaka.
The animation is not all that impressive and the voice cast is limited as is the case with most shorts, but it still doesn't take away from the characters or the story. The brother and sister pair well together (as true brother and sister).
Namika (the little sister) is cute, lovable, and 100% Osakan, Kyousuke (the brother) generally
goes along try to make sense of his Osakan little sister, and Kaede (the Little sister's best friend) helps round out the cast.
I went into watching this having little to no expectations and upon completion was astounded and highly entertained. This anime short contained likable characters, was very humorous, extremely entertaining, and a must watch in my opinion. Trust me you won't regret it.