The one that Julia Louis-Dreyfes wore was the black sleeveless dress with the white stripe down the sides. I am pretty sure, though, that they were on different talkshows.
The green and white top that Lauren wore with the white pants when she and Jeff Daniels were on the view was also worn by the british gal that was on the last Jenna Elfman show (she was also on Ugly Betty). I am pretty sure that someone else wore it as well. There have been several Lauren outfits that have been worn by other people since GG days.
Ha it went the other way around once that I know of where Lauren/Lorelai wore a top that Jennifer Aniston as Rachel wore. It was the black short sleeve sweater that had the white cuffs at elbows and white collar. Lorelai wore it to the Gilmore's house when she and Sookie went for the tasting for Richard and Jason's party then stopped by Luke's and Kirk was there practicing for his date with Lulu.