Jack's website www.justjack.com really does exist. It now redirects you to NBC's Will & Grace website, but at the time it was created, it was an actual web site created by "Jack." It included pictures and a letter Rosario wrote to the INS.
Originally Max Mutchnick and David Kohan pitched a straightforward couples comedy in which a gay man and his straight female roommate were supporting characters. NBC liked the supporting characters better.
As revealed in an interview, when Megan Mullally learned she won the role, she was leaving NBC studios and made an illegal U-turn. She was pulled over but said it didn't matter because she's on a new show.
Karen Walker's husband, Stan, is never entirely seen. However, in Will & Grace: New Will City (2000), viewers do get to see parts of Stan Walker. He reaches out and grabs Karen's breast while she is talking to Will and throughout the scene viewers can see Stan's legs though most of him is blocked by a plant.
Because of the show's numerous pop culture references, many of the celebrity guests had already been mentioned on the show before their eventual guest appearances (e.g., Alec Baldwin, Matt Damon, Madonna, Britney Spears, etc.)
During the episode in which Will and Grace compete for the Tenants Association Presidency, one tenant complains that her missing umbrella closely resembles the one belonging to "Tim Kaiser in apartment 12-B." Tim Kaiser was a producer of the episode.
In the episode where Grace is going to meet an old high school crush, he says he's part of a group of artists showing their art at the Zelman Gallery. Debra Messing's (Grace) real-life husband is Daniel Zelman.