Season 3 - missing episode on dvd

Sounds like it might be a Region difference based on local laws regarding gambling or some odd quirk of the guest star contracts that prevented them from being able to include it. Mostly you see this with music, where copyright owners let the series use a particular song for a fair price during original airing, and then want an exhoribitant amount before they'll okay it for use on a DVD release of the same show, often to the point where the studios claim it would be impossible to make any money just for paying the rights on a single song (particularly if it was used in the credits). The one instance I can think of regarding character contracts is that there are green-clad twins who appear in the Cantina scene of Star Wars who have never been released as action figures (despite the high desire to see them produced) because the actresses who played them had some odd clause in their contract that allows them to either demand enough money for the use of their likeness that Hasbro will never agree to pay for the right to produce them, or to simply deny them the right to do so with money never even coming into question. The one character who only appears in this episode is Hairy Head (not sure who that is), played by Ned Dennehy, but he doesn't seem to have the kind of career that should have allowed him to have that kind of clout, so I'd guess it has more to do with the gambling aspect.