Forest of the Dead (2) - S4-E9
Visible crew/equipment: When River punches the Doctor, laying him out, just as he drops to the floor we can see the actor's green tape mark at River's feet. (00:33:20)
Continuity mistake: When Katara is trying to heal the wounded earthbender, she gives Sokka the idea to take down The Drill from the inside. Sokka then stops her from saying anything while she is sitting down, and she is wearing her necklace. When she stands up in that same shot, the necklace is gone, like they forgot to animate it. (00:07:35)