Ep 4. There Is 1 Second Before the Demon Lord's Floods Burst Forth

When Oga wakes up one morning, he's floating in a great pool of water... However it is actually Baby Beel's pee, as it is "urination season" right now in the Demon World. Oga is concerned about the entire city being inundated and humanity's imminent destruction, so he takes Baby Beel to the drug store to buy some disposable diapers. While he's there, a bunch of bank robbers a take Oga, Baby Beel, Hilda and Furuichi (who were chasing after him) as hostages.