Simulated pregnancy

A simulated pregnancy is a deliberate attempt to create the impression of pregnancy.
It should not be confused with false pregnancy, where a person mistakenly believes that they are pregnant.
Techniques.
People who wish to "look" pregnant, generally for social, sexual, entertainment, or psychological purposes, have the option of body suits and the like to wear under their clothes. It can be done by using pillows or pads, or light-weighing, small balls with a round shape to simulate a pregnant abdomen. A common practice is to place a form replicating a belly (rolled up clothes, deflated ball, etc.) under a skin colored, tight bodysuit. This creates a realistic color and shape.
Reasons.
A female character lies about being pregnant. This can be done for a variety of reasons: perhaps the character is trying to get her boyfriend not to break up with her due to a misguided belief that Babies Make Everything Better; perhaps (conversely) she is trying to scare her boyfriend off; perhaps she is trying to get another character to give her unofficial child support. This could also be done as part of a Family Relationship Switcheroo (in which, for example, a daughter gets pregnant out of wedlock, and her mother fakes a pregnancy in an effort to pass the baby off as her own, rather than her daughter's). In historical dramas, this might also be done to stave off a capital sentence, as it used to be forbidden in Europe to put a pregnant woman to death.
In Popular Culture.
In "Desperate Housewives", Bree Van de Kamp fakes a pregnancy to keep people from finding out that her daughter, Danielle Van de Kamp is actually pregnant. 
In Passions, Pretty Crane fakes a pregnancy to keep her sister, Fancy Crane and her and Fancy’s love interest, Luis Lopez-Fitzgerald from getting married.