Sentence 1: My wife always joked I was in the slug club at work. 
 Sentence 3: My boss only likes to take certain people out to dinner 
 Sentence 4:  He has a group that he considers his inner circle 
 Sentence 5:  But since I'm in the slug club I get to enjoy great meals 
 Given Sentence 2: It is a reference to the club mentioned in Harry Potter.