SUCCESS!!! I FIGURED THE DARN THING OUT!!!!
Ok... so take the arms off at the elbow like Robbie said. I was only able to get the left arm off at the elbow leaving the elbow joint attached, but I was able to completely remove the right forearm/elbow joint. The KEY thing is to be able to remove the forearm/elbow joint of at least one side.
Step 1: Lift the shorter arm (Only bicep attached) straight up.
Step 2: Slide the body feetfirst through the neckhole as Robbie said, but make sure to slide the longer arm facing downward through a sleeve.
Step 3: Now move the longer arm (That is now in the sleeve) upwards and slide the shirt over the shorter arm by having the shorter arm point straight up!
Basically get the first arm through the sleeve along with the body. Once the arm is through the sleeve, move the shirt upwards over the shoulder and slide the other arm (Really the bicep) through the other sleeve.