As Lisbon and Jane arrive at the zoo, there is bright sunlight and the road is dry. Seconds later, inside the zoo, there are big puddles everywhere.
When Grace and Patrick look for the missing boys, Marvin Pettigrew says, "Missing 63 days," but when Patrick goes to see the kid's mom she says he has been missing for 61 days.
When Volker is at the zoo looking for Marvin Pettigrew, he grabs a little boy (the one in stripes) outside the reptile house, thinking it is Marvin. Moments later, as Volker walks into the reptile house, the same young actor is inside, reflecting off the glass of a display enclosure.
When Patrick goes to meet Volker at the school. Volker is "reading" a story to the children. When the camera angle is such that the pages that he is reading from are visible, it is clear that the page is blank.
At 8.35 after Lisbon gets Volkers DNA sample and walks away. As the camera tracks her out it pans behind Volkers chrome chair and you can see the cameraman reflected in it.