In 2015, Mayfair Games (makers of "Settlers of Catan") launched a Kickstarter campaign to produce a real, playable version of "Cones of Dunshire." The Kickstarter failed, because for a $150 pledge, you got a deluxe game...box. The actual game required a $500 pledge.
Among the Japanese paraphernalia in Councilman Jamm's home is a poster written in Kanji (visible over his shoulder as he cooks scrambled eggs on an authentic Benihana table). The poster translates as "North Korea"
The sleeve patch on right arm of Chris's referee shirt is the sleeve patch for the "UEFA Champions League," a Europe-wide football (soccer) competition for the best teams from each of Europe's top football (soccer) leagues.
Donna is wearing the same clothes in the picture on her real estate business card as she is when she shows Ron the card.
Leslie asks Councilman Jamm "you enjoy the ancient art of karaoke, yes?" This is almost identical to a line Amy Poehler's character has in Baby Mama (2008): "I was just practicing the ancient Japanese art of karaoke".