Mrs. Howard, the demented patient who shoots up the ER, appeared in Season 6 ("Leave it to Weaver") and died because of an accident in a coffee shop. She shows up again with the same name, very much alive.
While Rena is helping the little boy through his medical exam, in one camera angle, she is holding the bottle of bubble solution. In the other angle, the little boy is holding it. The scene switches back and forth between the two angles.