Also called a continuation, a sequel is a fanfic written to show events that occur after the end of another given fanfic, either the writer's own tale or someone else's. The sequel could also show events happening after an episode in the canon Dariaverse, over a time period that is otherwise not described. The fanfic or episode on which the sequel is based is self-contained and does not require the sequel, which could still tie up loose ends from the original story or expand upon minor plotlines. The implication is that a sequel is like an afterthought, and was not conceived until after the original episode or story was presented. A post-canon story is often a direct sequel to Is It College Yet?, following Daria characters as they go to college.
An example of a canon sequel would be "A Tree Grows in Lawndale", which is a sequel to Tommy Sherman's death in "The Misery Chick". In the story arc covering the triangle of Daria, Jane, and Tom Sloane, "Fire!" is a sequel of sorts to "I Loathe a Parade," "Dye! Dye! My Darling" a sequel to "Fire!, and Is It Fall Yet? a sequel to "Dye! Dye! My Darling." Is It College Yet? serves as a sequel to Fall, using the same naming scheme, showing the end of the Daria/Tom relationship that the first film started, and including another Landon summer party.
An example of a fanfic sequel to a show episode would be TAG's "Sudden Death Overtime," which immediately follows events in the fourth-season episode, "A Tree Grows in Lawndale." A fanfic sequel to another fanfic by the same author would be E. A. Smith's "The Tempest," which follows his Love's Labours Trilogy. A sequel written by one author for a fanfic by another author would be Chris Smith's "More Than Anyone Can Take," a follow-on to "Maine Escape," by Michael Pfeffer.