The basketball that contained the gibbon changed colors between Cragen getting a hold of the ball and actually opening it to rescue to animal.
When the ER doc is talking to Benson, he says "the first bullet went through and through and the second went in his bicep" referring to Eliot. But when Stabler is comforting little Eliot there is no exit wound on his back.
At 31:12, blood can be seen on Detective Stabler's sweatshirt in the upper left shoulder area. It is clearly above the seam that spans across his chest. However, at 31:22 the blood stain has moved farther down his sweatshirt, directly on top of said seam.
O negative blood can be given to anyone regardless of their blood type. For that reason it is often used in the ER when the recipient's type isn't known and there is no time to test.
In the beginning of this episode the ER doctor says he needs "O neg" blood for Stabler but in season 8 episode 9, at the end of the episode, Stabler and Benson are waiting for an elevator and state their blood type to each other as "A pos". Correction: O negative blood can be given to anyone regardless of their blood type. For that reason it is often used in the ER when the recipient's type isn't known and there is no time to test.