The first time Kurt drives the Ford van, it makes the starter and transmission solenoid sounds of a Dodge Caravan. The second time, the exhaust sounds like a 4-cylinder engine, even though the van has 8 cylinders.
After Greg trips over the wire at the party, while Charlotte is singing, Kurt is standing next to his wife. When the camera jumps back showing all of the party guests, she is gone. When Charlotte stops singing, and Kurt asks her how she learned to sing, his wife is standing next to him again.
The title belt worn by "Hulk Hogan" at the '80s party was in fact the WCW World title, known as the "Big Gold Belt". This would not have been the belt worn by Hogan in the time period as he was with the WWF and their world title was the famous "Winged Eagle".