Talk about hanging on a punchline. In May 2009, Twitter user @DrFNFurter started a joke, one that wasn't completed until May 2014.
In keeping with their username, it was a Rocky Horror Show gag. You know. Time warps, and all.
Note the gap in the date between the last two. Well played.
'Rocky Horror' Fan Time Warps 5 Years to Complete a Tweet [Mashable]