Fortunately, Ken Collins, who served as second assistant director for the shooting, responded to a request from Al Yellon to clarify the situation:
I was the second assistant director on the movie. That’s me sitting in front of Ferris and Cameron wearing Raybans and a Cub cap. I put myself into the scene as an extra. Being an L.A. guy, I had wanted to wear a Dodger cap but John Hughes said no way! We started our shooting in Chicago on September 9, 1985.
We definitely were at Wrigley on a game day. We started around 10am filming actor closeups and dialogue with a bunch of our extras in a specially designated part of the bleachers. When the game started, we grabbed some shots over the actors connecting them to the game and then we pulled out and moved up the street a couple of blocks to continue filming another scene. We left a camera behind to pick up some miscellaneous shots. We were close enough to the stadium to hear the crowd roaring and a lot of us continued to listen to Harry call the game. It got colder and windier and the game turned into a typical Wrigley slugfest where over 30 runs were scored. I’m pretty sure that the game was played on Sept. 24, 1985 and the Cubs lost to the Expos 17-15.
We filmed the famous Danke Shoen-Twist and Shout sequence at the Von Steuben’s Day parade on the following Saturday.
So that settles it.