Revealing mistake: In the episode where Teri Hatcher's character is in the supermarket, as you see her place her two items, a carton of OJ and a carton of eggs, listen closely. The items are empty -- quite obviously so. (00:17:45)
Sunday in the Park with George - S1-E21
Revealing mistake: When Morty gets down on his knee to propose to Sophie, the angle of the camera shows the top of the set, which makes it seem as if there is no ceiling to the room.
Answer: Kayla was sent away in episode 16 (The Gun Song) in season 4, after falsely accusing Lynette of child abuse. She now lives with her grandparents - probably Nora's parents.
I'm curious why we never see her again, why she never talked about, and why Tom never mentions visiting her.