I don't really have one, but a while ago while watching the episode D.W. Bossy Boots I noticed several things right off the bat. The large presence of 4th Graders there (as well as Jenna). I'm going far out on a limb by saying this, but I don't think any of those 4th graders (except Brian and John) have any siblings at that party, so that was one thing I noticed.

Also D.W.'s cousin was seen there. Did D.W. even know she was there at all? This is one of these things that do need an explanation. Sure there maybe holes in that, but one thing I can say. When we last saw D.W.'s cousin in Arthur's Cousin Catastrophe D.W. did not meet Emily until later on in Season 1. Unless ACC was a prequel I don't think her cousin knew Emily. That alone along with the other 4th Graders being there is two things I found interesting about that episode. These images show D.W.'s cousin by the way.