"8 pounds and 21"" joke

A young couple are on their way to Vegas to get married. Before
getting there, the girl said to the guy that she has a confession to
make; the reason that they have not been too intimate is because
she is very flat chested. If the guy wishes to cancel the wedding,
its okay with her.
The guy thought about it for a while, and said he does not mind she
is flat, and sex is not the most important thing in a marriage.
Several miles down the road, the guy turned to the girl and said
that he also wants to make a confession; he said below his waist, it is
just like a baby. If the girl wants to cancel the marriage, its okay
with him. The girl thought about it for a while and said that she
does not mind, and she also believed there are other things far more
important than sex in a marriage.
They were happy that they are honest with each other. They went on to
Vegas and got married. On their wedding night, the girl took off her
clothes; she as flat as a washboard. Finally, the guy took off his
clothes. One glance at the guy's naked body, the girl fainted and fell
to the floor.
After she became conscious, the guy asked: "I told you before we got
married; why did you still faint?" The girl said; "You told me it was
just like a baby". The guy replied: "Yes, 8 pounds and 21 inches".