STOP making eye contact with this guy. As you look at him you are giving him permission to "enter" conversation. Just tell him you are busy, and if he doesn't get the message after a couple of tries, let your boss know and use the phrase "harrassment" in the conversation. By law, the boss must intervene.

Your boss should be able to do as he/she pleases, as long as the actions do not cause an unsafe, or customer related event. Sounds to me that you may be jealous/envious of this person, who has decided to enjoy life and make the most out of a light-hearted situation. Are you telling me that you don't fart? Are you one of those who runs to the bathroom to fart, spending time away from your job and still getting paid? Come on......YOU need to grow up!