Groan alert: 
 
Two surgeons and a dermatologist were having lunch in the hospital cafeteria when the first two doctors began to laugh hysterically. 
 
“What’s so funny?” the confused dermatologist asked. 
 
“I’m sorry, you wouldn’t understand,” said one of the surgeons. “It’s an inside joke.”

One Liner
On a maternity room door: Push. Push. Push.