When Marlo Thomas turned up as Rachel Green’s mother on “Friends,” ’60s TV aficionados had a good laugh at the appropriateness of the casting, since Ann Marie – Thomas’s character on “That Girl” – could easily have been Rachel’s mother, given all of their similarities. By the fifth and final season of “That Girl,” things had finally gotten serious between Ann Marie and her longtime beau, Don Hollinger (Ted Bessell), with the two of them at long last getting engaged…not that we actually saw them tie the knot by the end of the series. (Apparently, Marlo didn’t want to send a message to young women that marriage was the ultimate goal for them.) Virtually every episode this season features a recognizable guest star, but some of the bigger names include Cloris Leachman, Regis Philbin, Alex Rocco, Dick Van Patten, Milton Berle, and Marlo’s daddy, Danny. Meanwhile, fans will be glad to find that Marlo has returned, along with series co-creator Bill Persky, to contribute a foursome of audio commentaries, including one for the final episode. Kudos to Shout Factory for successfully putting out the entire series of “That Girl” onto DVD; it might not be the funniest sitcom of the ’60s, but it’s an important one that deserves to be remembered.