The Joker's Flying Saucer - S3.E24

The Joker is back in Gotham City, this time with his sights set on worldwide domination. He plants rumors of an invasion from outer space, then sets out to gather the Beryllium metal needed to build an actual flying saucer. Batman picks up on his scheme and sends Alfred to check up on a stash of the metal. But when Alfred is mistaken for a mad scientist by the Joker, he is hauled off to the villain's lair along with Batgirl. The Dynamic Duo are on their way when a bomb planted by one of the Joker's henchmen goes off, leaving them unconscious, and their Batcave cut off from the rest of the world.