I know that in Perfect Strangers, the Welcome to Chicago sign leaving ORD appears in the first season and in the remaining seasons when the long opening sequence is aired. The short of the later seasons omits that, however its shown out of context in season one.
Season one opener shows the two star characters traveling from their homelands to the big city. Larry Appleton, who drove his Mustang from Madison, WI to his new home is shown passing under the I-190 Welcome sign which means to actually transit by it, you have to take a detour into O' Hare to accomplish that as no through roads lead through the airport to reach it especially if you take I-90, which is the main route from Madison to Chicago other than both US 12 & 14 that also do the trip, but none place you inside the airport to reach I-190 East.