A chair and a pillow.
Lots and lots of practice
You open with a doctor’s assistant standing by a chair in walks the hypocondriac (person who always thinks that they are sick) and complains to the assistant that his stomach is hurting.
She tells him to sit in the chair. Soon another boy walks in and tells her that his arm is broken. The hypocondriac stands up and acts as if his arm is broken too. You repeat this process with different injuries every time until all boys have gone except for one.
The boy playing the hypocondriac acts out each of the injuries everytime. Then the last boy comes in with the pillow under his shirt and in a funny way says “I’m Pregnant.” The hypocondriac stands up and says “I’m Pre…” stopping short and just walking off stage.