"Helter Skelter" was a storyline by Garth Ennis, featuring an invasion of Mega-City One by an alliance of villains from parallel universes.Due to the distortion of reality, characters from dozens of 2000 AD strips made cameo appearances, either in the background or as parts of the plot (Dredd is attacked by the vampires from "Fiends of the Eastern Front" and then has to avoid Old One-Eye from "Flesh").