Humorous joke: Are you the foundation? My friend said in black that you still called me.

My cousin tells you a story: My friend's name is Wang Yuanji. One day he went to see his girlfriend's parents for the first time. His girlfriend's father greeted him warmly: "You must be Xiao Wang!" " "When I thought about it, I felt it was wrong, so I quickly changed my mind:" You are Xiaoji! " Seeing that the atmosphere was getting more and more embarrassing, his girlfriend and mother hurried out to make a circle, glanced at the old man and said, "What the hell is that?" "Then take your colleague's hand and say: You are the foundation!" My friend looked at the black line and said, "Call me Xiao Wang."