This is my favorite mother joke. Actually it's a mother-in-law joke and it comes from the very politically incorrect but screamingly funny AMOS & ANDY SHOW. I believe this was written by Mosher & Connelly (who went on to create LEAVE IT TO BEAVER and THE MUNSTERS).
The Kingfish sets up a blind date for "Mama". Hoping the poor guy would like her and take her off of his hands he arranges for Mama to go to the beauty parlor. He's talking to the hair stylist, describing Mama. He says (and I'm paraphrasing), "Picture a grapefruit that's been out at sea. And it washes ashore, all covered with seaweed and crabs. Now it sits in the sun for a couple of weeks and gets all wrinkly and rotted and bugs are now flying around it. Can you picture that?" The hairstylist says "Uh huh." And the Kingfish says, "Good. If you can make her look that good I'd be satisfied!"