Nelson Mandela could be a cheeky chappie (witness his description of meeting the Spice Girls "I don't want to be emotional but this is one of the greatest moments of my life,") and his sense of humor was at play whenever he met the Queen.

Not one to stand on ceremony, he would call her by her first name, Elizabeth, and even sometimes commented on her dress and weight, according to a personal assistant quoted by Reuters today.
Zelda La Grange said, "When he paid visits to Queen Elizabeth it was always very interesting to see their interaction because he called her 'Elizabeth', no-one else in the world calls her Elizabeth, I think.
"He would comment on her dress and her weight, and you don't do that with the Queen," she said.
The Queen was apparently not offended, "She really adored him" and "quite enjoyed it" La Grange said.
Prince Charles is representing the Queen at Mandela's funeral on Sunday. The Queen no longer flies long-haul.