What jokes did you understand after reading Water Margin?

Cao Cao pointed to Liu Bei with his finger, then pointed to himself and said, "Only the monarch and Cao Er are heroes in the world today!" Liu Bei was taken aback. The spoon in his hand fell to the ground. ...

It is also a coincidence that those chopsticks fell at Liu Bei's feet. Cao Cao quickly crouched down to pick it up, only to see a pair of big-eared, pointed feet sticking up on the edge of chopsticks. Cao Cao didn't pick up chopsticks, so he went to squeeze on Xuande's embroidered shoes. Liu Bei laughed and said, "Don't ask Luo Chan! Do you really want to fix me up? " Cao Cao knelt down and said, "Just to make you a Cao Er." Then Liu Bei put his arm around Cao Biao and lifted him up.