In the opening credits of a TV show, I have seen that sometimes on the last actor/actress, they will get an "and" before their name. An example that comes to mind is on It's Always Sunny In Philadelphia, Frank is credited with "and Danny DeVito". Why do they do that, what is the purpose of it? What determines if a cast member is worthy of the "and"? I know there is this question about "with"; do the same rules apply for "and"?
When credits are usually presented, the main players will usually be credited first (either in terms of stature or character importance, unless the piece is a true ensemble of the highest calibre, where they usually plump for alphabet?). Once they are done with in 'descending' order, any supporting players of note will be highlighted at either the very end, or at the beginning of a 'second tier' of credits of supporting actors and / or guest stars with the most recognisable names preceded by an 'And', 'With' or 'Guest Starring' to highlight them over the rest of the cast.
Of course, having for too hastily posted this without reading through the much better explanation you have provided the link to, contractual agreements will have a huge bearing on the specific positioning of the individual names. To cite a couple of films instead of T.V. Shows, note that neither Christopher Reeve nor Michael Keaton received top billing on either the Superman or Batman films until the sequels.