Penny:  You are a grown man . Haven't you ever been sick before ?
Sheldon Cooper: Of course . But not by myself .
Penny: Really ? Never ?
Sheldon Cooper: Well , once , when I was _ fifteen _ and spending the summer at the Heidelberg Institute in Germany .
Penny: Studying abroad ?
Sheldon Cooper: No , visiting professor . Anyway , the local cuisine was a little more sausage - based than I 'm used to , and the result was an internal blitzkrieg , with my lower intestine playing the part of Czechoslovakia .