Three students at Lawndale High, The Three Js are boys obsessed with one of their classmates, Quinn Morgendorffer. Quinn was only able to remember the names of Joey and Jeffy, often calling Jamie "Jameel", "Jason," and other names that began with "J." Ironically, Jamie is the only character to be given a last name in canon.
In the shooting script for "The Invitation", they're described as "three nearly identical jockboys".
Though in competition with one another for Quinn's affections, and having come to blows in The Invitation, the characters appear to share the same brain, and together are almost smart enough to be considered a single person of only marginally-below-average intelligence. They often appear to think as a collective, such as in Groped by an Angel, when they manage to collectively arrive at the conclusion that Quinn's "guardian angel" is actually a human suitor who is "way too old for her." They also convince themselves, somehow, that Timothy O'Neill, the "Language Arts" teacher, is Quinn's guardian angel.