If you follow the link in the tweet, you'll go to another person's twitter account, which has a picture of The Mona Lisa photoshopped in with the male twitter user's stubbled face. To which Nolan North replies, "wow Caitlyn Jenner really let herself go." Now, regardless of how North actually feels about transgender individuals or Caitlyn Jenner specifically, it's a joke in poor taste, especially for a topic that carries an incredible amount of emotional baggage. Regardless of whether or not he meant to offend, it is an offensive joke.