In the comics, Xotar is a male villain who first appeared in Brave and the Bold #29 (May 1960). He traveled from the future and used stolen advanced weaponry to fight the Justice League in their first battle as a team. Xotar has appeared sporadically since then.
In the final season of Supergirl (2015), Alex adopted a daughter, Esme, an alien with powers similar to Kramer's meta-mimicking abilities.
When Barry arrived in the Hall of Justice, the leitmotif from when he unveiled the hall to the Crisis team in Crisis on Infinite Earths: Part Five (2020) can be heard.