Complex sentence: Yellow Lantern and the alternate Hawkgirl mistake Batman for their own and apprehend him, while the Joker allies himself with the alternate Harley Quinn, who has founded an underground organization called the "Joker Clan" to honor her Joker.
Split into simpler sentences: Yellow Lantern and the alternate Hawkgirl mistake Batman for their own and apprehend him. The Joker then allies himself with the alternate Harley Quinn, who has founded an underground organization called the "Joker Clan" to honor her Joker.