Robert's character wasn't retarded; he was educated in (I think) Saudi Arabian language and customs, then there was a screwup and he got sent to Los Angeles. So he didn't know the English language all that well, and his knowledge of customs and etiquette was deficient too. (I guess anyone new to North American culture will be considered retarded by us -- very sad.)
I loved the initial movies and TV series, although it scared the crap out of me as a kid! And man, that Diana was such a babe (for a lizard, of course!).
The new leader of the Visitors will be played by Morena Baccarin (from Firefly), and her character's name is Anna. I can't imagine she'll be quite as cool as Jane Badler, who played Diana, but at least she's easy on the eyes too.
cheers,
supervij