S1, E4: When Oga wakes up one morning, he's floating in Baby Beel's pee, as it is "urination season" now in the Demon World. Oga is concerned about the entire city being inundated, so he takes Baby Beel to the drug store to buy disposable diapers. While he's there, a bunch of bank robbers take Oga, Baby Beel, Hilda and Furuichi as hostages.