Crossovers
In the third season of Batman Beyond, a two-part story entitled "The Call" featured (for the first time) the futuristic Justice League, a springboard for Bruce Timm's next series Justice League. The setting and characters of Batman Beyond were also briefly revived in 2004 for an episode of Static Shock in which Static is accidentally transported 40 years into the future.
Justice League Unlimited revisited the world of Batman Beyond twice in 2005: The first time was in the first season finale which featured the Justice League (Batman, Wonder Woman and Green Lantern) transported 50 years into the future to stop a time-travelling villain with the help of the future Justice League Unlimited (Terry as Batman, a future Static and Warhawk). The second time occurred during the second season finale where Terry McGinnis's true secret origin is learned in a story meant to be the de facto series finale for this Batman's story.
Read more about this topic: Batman Beyond