A classic favorite of mine.
A little blonde girl comes back from school one evening.
She runs to her mum and says: "Mummy today at school we learnt how to count. Well, all the other girls only counted to 5, but listen to me: 1,2,3,4,5,6,7,8,9,10! It's good, innit?"
"Yes, darling, very good." Answers the mom.
"Is that because I'm blonde?" she asks.
"Yes, darling, it's because you're blonde." The mom says.
Next day, the little girl comes back from school and says: "Mummy, today at school we learnt the alphabet. All the other girls only went as far as D, but listen to me: A,B,C,D,E,F,G,H,I,J,K! It's good, innit?"
"Yes, darling, very good." Answers the mom.
"Is that because I'm blonde, mummy?" she asks.
"Yes, darling it's because you're blonde." The mom says.
Next Day, she returns from school and cries: "Mummy, today we went swimming. Well, all the other girls have no breasts, but look at me!" She proceeds to flash her impressive 36D at her mummy. "Is that because I'm blonde, mummy?"
"No darling, it's because you're 25."