Humorous joke: Is this glass a magnifying glass?

Humorous joke: Is this glass a magnifying glass?

Some people are well-known in the city because of their obesity. One day, while he was drinking in a bar, a foreigner came in and stared at the glass door of the bar carefully. The fat man was very angry because he noticed that people outside were always staring at his own shadow. Just before the attack, the foreigner suddenly knocked on the glass and asked the guy in the bar, "Hey, man, is this glass a magnifying glass?"