The Capitol City Monopoly is a board game which is very popular in Capital City.
After Bart had understood that Lisa was mad at him, he wanted to play the game with her. Lisa refused, so Bart threw the dice for her which let her pick up all the chance cards. Lisa then learned that Bart had replaced them with cards he made. They contained nice things he will do for her on them, and the two hug.
Behind the laughter
It's a parody of Monopoly.