A.I.: Artificial Insemination is the two-part season finale of the fourth season and 92nd episode overall.
The first part deals with Will and Grace's decision to have a baby. The second part deals with each of the main characters facing dilemmas about the future of their families and career.
Will and Grace's familyWill and Grace try to keep their plan of starting a family a secret from Jack and Karen but soon find out they each have told the other anyway. At their first try at IVF the bag containing Will's sperm gets mixed up and Rosario ends up mopping the floor with Will's sperm. After another failed attempt, they try to get Grace pregnant naturally but could not push through because Will is gay and according to Grace, "sex changes things", including their friendship.
On their way for another try at the fertility clinic, the taxi they are in breaks down so Grace runs through Central Park with Will's sperm to make it to their appointment but is distracted by Jack and she runs into a lamp post, knocking herself out. She wakes up to the silhouette of a man in a horse.
After being rejected in his previous audition and getting promoted to floor manager at Barney's, Jack decides to quit acting for good. While celebrating in his new office, he gets knocked out by falling boxes and dreams about God encouraging him to follow his bliss, which is show business. Jack wakes up with an epiphany to quit his job and go to another audition instead.
Karen has been lonely since her husband Stanley went to prison. A charming rich man named Lionel Banks approaches her at a hotel bar and propositions her, mistaking her for a prostitute. When he asks Karen if she is married, she lies and tells him she is not. She eventually admits that she is married however Lionel says that he does not care and then hands her the key to his suite before leaving. Karen feels tempted to follow him.
- Eric McCormack (Will Truman)
- Debra Messing (Grace Adler)
- Sean Hayes (Jack McFarland)
- Megan Mullally (Karen Walker)
- Shelley Morrison (Rosario Salazar)
- Cher (Herself)
- Rip Torn (Lionel Banks)
- Laura Kightlinger (Nurse Sheila)
- J Lucas (Ruben)
- Andrew Rosenbach (Terry)
- Charles C. Stevenson Jr (Smitty)
- Peggy Lane O'Rourke (Female Cabbie)
- Richard Assad (Male Cabbie)
- Jack's old boss Dorleen is mentioned getting fired after going to rehab.
- Karen says that Lionel Banks is the bass player of her Lynyrd Skynyrd tribute band, famous for their song Sweet Home Alabama.
- Rosario orders P'Zone, the pizza calzone offered by Pizza Hut.