Revealing mistake: Watch very closely when the horse is waking up Atreyu. It seems to be searching for something behind Atreyu and then you see a sugar cube fall out from behind him.
Revealing mistake: When Atreyu is holding on to the tree as the Nothing attacks, you can see a string on his leg right before he yells out "Falcor!"
Revealing mistake: When Atreyu is talking to Morla, Morla keeps sneezing which keeps throwing Atreyu off the tree, but in one shot, right before Atreyu falls off, apparently it's his stunt double.
Answer: That's actually Urgl, Engywwok's wife. She is giving Falcor a vitamin injection while she is nursing him back from his exhaustion.
Twotall