"Sex in Bed" joke

A Chinese man arranges for a hooker to come to his room for the evening.
Once in the room they undress, climb into bed, and have at it. When
finished, the Chinese man jumps up, runs over to the window, takes a deep
breath, dives under the bed, climbs out the other side, jumps back into bed
with the hooker and commences a repeat performance.
The hooker is impressed with the gusto of the second encounter. When
finished, the Chinese man jumps up, runs over to the window, takes a deep
breath, dives under the bed, climbs out the other side, jumps back into bed
with the hooker and starts again. The hooker is amazed as this sequence is
repeated four times.
During the fifth encore, she decides to try it herself. So when they are
done she jumps up, goes to the window and takes a deep breath of fresh air,
dives under the bed,... and finds four Chinese men.