Madge appears as an "oddly confident 40 year old secretary" with whom Karen decides to move in after her divorce with Stan is finalized. Although things appear rosy at first between the two flatmates, they decidedly take a turn for the worse after both of them become interested in the same guy.
9. Glenn Close
Glenn played Fannie Lieber, an eccentric photographer who takes one, two, and finally three family portraits for Will and Grace, owing to the latter two's non stop neuroticism and vanity. Although it was a great performace, this guest spot gets bumped down the list as Lieber is indirectly responsible for planting the infamous baby storyline in Season 4 & 5 which sucked. ass.
8. Elton John
Appearing as himself ("It's a little bit funny...") Elton appears towards the ending of this episode warning Will not to dismiss the existence of an apparent "Gay Mafia". Worth it just to watch Elton pat Eric McCormack on the abs and praise him for his "flat stomach".
7. Patti Lupone
Feeling bad after abandoning Will at a gay bar, Jack decides to make up for it by having a tea date with scones in order to have a proper chat with his bestie. However his attention span is tested when one of his all time idols Patti Lupone sits right beside him. SHUT UP, PATTI LUPONE!!
6. Al Roker
It wasn't so much Al's appearance itself that made this episode - moreso the fact that his storyline led to a much talked about kiss between Will and Jack, who were both protesting NBC for cutting out a same sex kiss on one of their network shows. Incidentally, because of this episode, W&G became one of the first sitcoms to show a kiss between two men on network TV. (I couldn't embed the above link, follow it to watch the clip on Youtube).
5. Britney Spears
No sitcom was better at lampooning the whacked out Bush Administration during the early 00's, and this episode featuring Britney as Amber Louise (secretly hardcore lesbian Peg) proved this. She's living the DREAM!
4. Matt Damon
When Jack tries out for the New York City Gay Men's Chorus, he soon comes up against Owen (played by Damon) whom he begins to suspect is actually straight. He enlists the help of Grace in an effort to try and "in" him.
3. Michael Douglas
Honestly the 34 seconds above just make this entire episode.
2. Mira Sorvino
Probably the best episode in the entire series (I WILL FIGHT YOU ON THIS) in which Sorvino plays Leo's ex-girlfriend and the only woman Will had ever slept with.
I find that even people who aren't fans or who have never watched the show know about this scene. It's just too iconic. Tahhoohhm! Taaaohhhmm! TAAAAOOOHMMMM!
Source 1 | Source 2 | Source 3 | Source 4 | Source 5 | Source 6 | Source 7 | Source 8 | Source 9 | Source 10
Apologies for the quality of some of the clips - they were the only ones I could find!