Mummy's black sponge

Little Johnny sees his mother walk out of the shower and sees her womanliness.He asks her what it is and she embarassed replies, "Oh, that's mommy's black sponge."A few days later, Johnny spills a glass of milk on the floor and says, "Mommy, I need your black sponge to mop up the milk!"She replies, "I lost it, honey."A couple of days later, he comes running up to her and says, "Mommy, I found your black sponge!" Mystified, she says, "Where, honey?"Little Johnny says, "It's over at Mrs. Johnson's house, and Daddy's washing his face in it!