Which one are you referring to? I remember one where Ernie kept annoying Bert by saying how thirsty he is, so Bert tells him to get a drink of water so he does then at the end he says, "Boy, was I thirsty." There's also another one where Bert is sleeping over at his brother Bart's so Ernie calls him and asks what to do when he's thirsty and he ends up talking on the phone to Bert all night.