Wikia

Superman: Our Worlds At War is a massive crossover story arc, which deals with an invasion by Imperiex.

Heroes

Stories featuring Krypto, the Superdog
Silver Age Comic Books	Adventure Comics #210 (First Appearance) • "Krypto's Family Tree"
Modern Age Comic Books	World Without a Superman (First Appearance of Bibbo's Krypto) • Return to Krypton (First Modern-age Appearance of Kryptonian Krypto) • "Superman: Our Worlds at War" • Teen Titans #7 • Atlas
TV Series	Superman: The Animated Series (Cameo) • Krypto the Superdog • Legion of Superheroes (Cameo)
Prose	Starwinds Howl • DC Super-Pets! (Pooches of Power)

Stories featuring Doomsday (Edit this template)
Comic Books	The Death of Superman (First Appearance) • Superman/Doomsday: Hunter/Prey • Doomsday: Year One • The Doomsday Wars • Superman: Our Worlds at War • Doomsday Rex • Apokolips Now! • In the Name of Gog • Infinite Crisis • Superman: New Krypton • All-Star Superman • Reign of Doomsday • Reign of the Doomsdays
TV and Movies	Superman: The Animated Series • Superman Lives • Superman: Doomsday • Smallville, season 8 • Superman/Batman: Apocalypse