Jack

In-universe

 * Jack, a college bar owner who distributed Black Frost.
 * Jack, a Drama student mentioned in "Happy Anniversary".
 * Jack, a character from "Provider".
 * Jack Carlson, a police detective of Los Angeles Police Department.
 * Jack MacNamara, the co-owner of XXI.
 * Jack Mayhew, a Class of '99 student named Class Clown for 1999.
 * Jack O'Toole, a Sunnydale High School student and zombie.
 * Jack the Ripper, a vampire active in 1888.
 * Jack Willitts, a Hollywood producer and the father of Karinna Willitts.

Real world

 * Jack, a Tales short story.
 * Jack Conley, the actor who portrayed both Gib Cain and Sahjhan.
 * Jack Plotnick, the actor who portrayed Allan Finch.
 * Jack Stehlin, the actor who Francis Angleman.