If you copy the URL of a tweet to this web site (http://www.Tweet2Cite.com) it will automatically generate properly formatted citations in MLA, APA, and Wikipedia format.
I have heard it said that you should never cite tweets because they are not research. The way I look at it, many of my 140 character tweets are more relevant and creative than most of my 25 page peer-reviewed journal articles. Go for it. Even the ones in the #WTF category.