Three. One to post it, another to post a better punchline in the comment section, and another to repost it with the new punchline.
Interactive Joke of the Day Mug
Coffee Mug
His sc*aaarrrr*f Edit: I get it guys, you all have better punchlines than me.
Two. One to post the joke and one to post a better punchline in the comments.
Three. One to post it, the second to post a better punchline in the comments, and the third to complain that it's a repost.
Three. One to post it, one to make a better punchline in the comments, and one to repost it the next day.