Characters who disappeared
Why did Leslie's mom disappear after the episode with Ben's parents and the quilt? I understand why Ben's parents wouldn't be at the gala and their wedding, but Leslie's mom lives in town and would be very upset not being invited to the wedding. She was heard to be watching the kids in season seven, but we never see her after that.
Also, why wasn't Mark Brendanawicz considered to design the Pawnee Commons project? After all, he gave Leslie a set of plans on his last episode. Why not have him revise his plans to include a dog park? It would have been a great chance for Mark to meet Ben and for us to see what happened to him after he Brendanaquit.