insert his entire arm in his cock. As he does that he uses his other arm to try and open up that hole so he can rotate it.
Baxter after much manuvering manages to rotate his arm 90° with his shoulder at the slit. He wonders how horrible he looks but, couldn't quite see as his head was nearly inside of his cock. Straining his neck with his other arm he realizes that he could stretch out anything he needs to and thus he turns to his cock.
His cock was distended by an incredible amount even surpassing the width of his waist. Baxter was shocked by how inhuman he looked. Remembering the dildo back at the lab he thinks to the yoga ball and imagining how that would feel he reaches to it with his other arm still inside of him.
Right as he begins to insert it in he thinks, "What would it look like if I put myself in?" Now Baxter has a choice continue with the yoga ball, or perhaps do something outlandish like stick his head in.