Actually you can make several t.co links and merge it together to post it on a tweet. Actually the tweet that this thread linked to have 5 links itself. Simply merging many t.co links with text can make the longest tweet and it works! And 50+ paragraphs is too much for a single URI anyway.
EDIT: Seems now Twitter has fixed the bug and only shows the t.co link not the text or exact URL in the tweet! No more longest tweets! Only t.co links.
Yes, that tweet actually uses five shorten t.co links which only return the text not the url as the user have made link with texts not url! Normally t.co shortened url get expanded automatically in the Twitter since they introduce the TweetButton. In this case, the text that shortened using t.co showing here! I guess there is no validation practices are not in place in terms of shortening using t.co.
Change yourtext to whatever you want (make it more lengthy and use whatever language you want) and bang! The longest tweet created! It's working simply because of the validation error in the url shortening of t.co, I reckon! Hope this might be fixed very soon. But, until then you can make longest tweets after all! Happy tweeting.. oh. happy looongest tweeting!!