Damn, Fury's a badass:

Maintaining perfect focus in the intestines of a living being.
Not wholly losing your stomach and possibly suffocating because the inside of a bear would be filled with a stench so wretched that you would effectively be forced to throw up.
Not losing consciousness because the likelihood of the internal sphincter tightening around a foreign body and effectively cutting off oxygen flow.
Being able to build up energy for a powerful magic attack inside of a bear, while all of this is happening
Not being affected in any way from being on the inside of a still living creature.