I caught part of that episode with Jennifer Coolidge the other night. Wow, she looks different! I know it's been at least a decade, but she looks like a tranny, now. I would not have known it was her if not for your post.
Courtney Cox played his girlfriend in the "syrup /dry cleaning" episode.
James Spader was already famous when he guest starred in the episode where George hounded him for an apology.
The older chick from "Just Shoot Me" played the doctor with the 60's hairstyle who wouldn't refund George's money.
Roz from "Frasier" was in one of the episodes. I don't remember what it was about, but I remember Jerry was at dinner with his parents and his mother described her as stunning and Jerry corrected her and said she was only attractive.
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Did anyone besides me ever notice that Jerry always had to have the most attractive girlfriend? Even during the weeks when George had a really good looking girlfriend, they would step Jerry's girl up a notch.
This reminds me that Sarah Silverman played Kramer's girlfriend during a few episodes.